We see the questions all the time – people wondering: What will it take to run an RV air conditioner off of solar power?
We get asked for advice in email regularly, and see the topic constantly coming up on various forums. (And now the Wynn’s are claiming they’re doing it – they’re not really, see below.)
Usually those asking are honestly naive about what will be required – assuming that a small investment in a few hundred watts of solar panels and maybe an extra battery or two is all that it will take to be basking in off-grid cold air all summer long.
I hate to be a destroyer of dreams, but…
Running an RV air conditioner exclusively off of solar power is a fantasy that is extremely difficult and expensive to turn into a reality.
As anyone who has ever paid a residential electric bill during a hot summer knows, generating cool air takes a lot of energy. Cooling an RV isn’t magically easier or cheaper – and in a lot of ways it is even more challenging.
Especially while trying to rely primarily on solar power.
Just consider a few of the things you’ll have working against you:
- Using roof-mounted solar panels means parking in the sun, and parking in the sun means that your AC has to work substantially harder to keep your interior cool.
- Solar panels absorb heat and get extremely hot while producing energy. Having panels on your roof on a hot summer day is like wrapping your RV in a heating blanket – forcing your AC to work even harder. Thin panels with no airspace underneath them will get hotter still – this is one of the reasons we decided not to go thin and flexible on our roof.
- Solar panels actually produce less energy as they get hotter, so on the hottest days when you need the power the most they are working less efficiently.
- By the way – your roof AC is now surrounded by extremely hot air radiating off the panels, further reducing the cooling it is capable of.
- Also – any shade your vents or roof AC casts on your solar panels will dramatically rob them of energy. A little partial shade on the corner of a panel can cut off the output of the entire panel. Most RV roof airs are not low-profile, and even low-profile AC’s can cast substantial shadows much of the day.
- Adding insult to injury – RV roof AC units are sadly NOT designed to be energy efficient, and are actually anything but – particularly compared to residential AC units. Most RV’s are not very well insulated either. The poor cooling efficiency and lack of insulation means that it takes a lot more power to keep the interior of an RV cool than it would to cool a modern well-insulated house of the same (small) size.
In other words – things are pretty bleak.
Cooling a conventional RV using a solar-powered AC is akin to pushing a boulder up a mountain… while wearing roller skates.
RV AC Power Requirements
Air conditioning units uses a lot of power – likely way more than just about all the other electrical devices you’ll find in an RV combined. The only typical RV appliance that rivals an AC in power consumption is a microwave / convection oven – but those aren’t on for hours at a time.
As an example, from our energy audit, we know that our two roof airs use this much power:
- Coleman Mach 8 15,000 BTU (Front AC): During this particular test, we measured 1,738W (136 DC amps) when on high cool, 1,631W (131A) on low cool, and 99W (7.5A) when the compressor is off but the fan is on. When we purchased this AC in 2013 this was the most power efficient low-profile 15,000 BTU air conditioner on the market, but that’s not necessarily saying a lot.
- Dometic Penguin 13,500 BTU (Rear AC): We measured 1,487W (116A) on high cool, 1,456W (114A) on low cool, and 296W (22.5A) when the compressor is off but the fan is on. This is a vintage 1989 AC unit that came with our bus, and is still running great.
When in use, an air conditioner blower remains on full time but the compressor pump cycles on and off. An AC is actually cooling air when the compressor is on, and just blowing a fan to circulate air when the compressor is off.
The compressor is the big power hog, and whether it is on or not is controlled by the AC’s thermostat. How much time an AC spends with its compressor on will vary dramatically based upon the outside heat and humidity.
The compressor also uses more power when the outside temperature is higher – so on a hot day the actual power consumed will be even higher than you’ll see if you test on a more temperate day.
On a hot summer day the AC compressor might be on non-stop fighting to keep things cool. On a summer night, it might be on 50% or as little as 25% of the time.
Doing a little math, you can work out an energy budget to come up with a range of how much power an AC might need over the course of a day:
- 100% Cooling Cycle: Our front AC would consume roughly 42kWh (kilowatt hours – this is the unit of measurement that electricity is metered and billed in) with 24 hours non-stop high cooling, and our rear AC would consume 35kWh. Fortunately there are few places that are so hot they would keep an AC running full-out 24 hours a day, because that is a ridiculous amount of power. At a common electric company price of 12-cents a kilowatt hour, both AC’s running full-out over the course of a day could cost $9.00 if on metered hookups.
- 50% Cooling Cycle: Cycling the compressor on only half the time, our front AC would consume roughly 22kWh, and our rear AC would consume 21kWh over the course of 24 hours. The front AC’s more efficient blower is starting to really demonstrate a power savings, but this is still a ton of power consumed.
- 25% Cooling Cycle: Cycling the compressor on only 25% of the time, our front AC would consume roughly 12kWh in a day, and our rear AC would consume 14kWh.
Leaving all other electrical loads out of the picture, it is easy to see that you could regularly need to generate over 10kWh a day of energy dedicated to running a single RV roof air conditioning unit – even if you only leave the AC on during the hottest part of the day.
To have even the slightest hope of powering this sort of demand purely via solar – this is what it would take:
- A Ridiculous Amount of Solar Panels: The amount of actual generated power you will get from solar panels will vary dramatically based upon your latitude, the time of year, the weather, and whether or not the panels are tilted optimally toward the sun. A 2,000W system, give or take, is a good start if you want to run an RV roof air for more than just a few hours a day. That’s 20x 100W panels – over 120 square feet of dedicated roof space!
- A (Half) Ton of Battery Capacity: To store 10kWh of power to get through a hot and muggy night will require roughly a 1,000Ah lithium battery bank, or 2,000Ah lead. You are looking at potentially 8x 8D batteries, and over 1,200lbs of lead on board if you go this route, and more if you want excess capacity to get through cloudy days.
- A Hefty Pure-Sine Inverter: An air conditioner should only ever be powered via a pure-sine inverter, and RV AC units have a substantial initial surge current so the inverter needs to be oversized to avoid overloading. To power an AC off of battery or solar power, an expensive high-end inverter capable of 3000W – 4000W output will be necessary, and you’ll still need to shut off the AC when simultaneously using the microwave or other high-current loads.
You could pay for a seeming infinite amount of generator run time, or years of camping with full hookups, for what building a solar system so powerful would cost!
In other words… don’t pursue solar air conditioning with any hopes of it saving you any money in the long run.
The Smarter Way To Stay Cool With Solar
One of the greatest advantages of living in a house with wheels under it is that you do not need to fight the weather – you can move!
Following temperate weather and moving north and south means that it is possible to mostly avoid hot and humid days when an air conditioner feels most necessary.
Moving to higher elevations when temperatures start to rise might be the quickest retreat.
Parking in the shade, covering windows with awnings, and using plenty of electric fans makes it often very possible to stay cool without needing to blow the energy budget.
Sleeping through the hottest part of the day and taking an afternoon siesta can work wonders too.
In a dry environment, a full-rig swamp cooler, or even a personal mister, can cool things dramatically without using much energy at all.
And on those few days when you really really really need some proper air conditioning, you have options:
- Field Trip: Spend the afternoon out shopping, or driving, or going some place where someone else is providing the AC. Mall walking is even an option if you get desperate. When we were stuck in Yuma during the summer once, we managed to come up with an excuse for a shopping trip nearly every single afternoon – just to find some cool air!
- A Brief Blast of Solar AC: If you have excess power available (and your inverter is configured to power your AC) an hour or two of AC in the afternoon might not blow the energy budget for the day. But be careful – your batteries will be draining fast! (This is the route we’ve gone with our setup – our 500AH of lithium batteries and 1400w of solar can give us some battery powered off-grid A/C.)
- Generator: Look, we hate the sound of generators… But if you are out boondocking and everyone else within earshot has given in and fired up, your not going to get a special “solar purist” medal for sweating. A few hours of generator time will top off your batteries and cool you down on a hot afternoon.
- Seriously, Just Go Pay For Hookups: If it is 100+ degrees out, stop trying to fight it. Rather than run a generator 24×7 to keep boondocking off the grid, go find a cheap RV park and pay for 50A service. Run all of your roof airs at once and chill out till the heatwave passes!
100% Solar RV AC Can Be Done – If You Design For It
If you really want to go generator-free, have air conditioning whenever you want it, and never pay for hookups… It can be done.
But you will need to design your entire RV around optimizing for this capability.
One of the few examples I have seen is the Over The Top Cargo Trailer – with 2250 watts of solar dedicated to the task of creating a 100% solar heated and cooled a 7′ x 18′ windowless box. It is an awesome project – but it shows just how hard it is to go 100% solar once air conditioning is in the mix.
If you want to go down this path, you will be doing it for the geek points – not because it is practical, or to save money.
As long as you know what you are getting into, here are some tips:
- Swamp Cooling: The cheapest and easiest and most energy efficient way to generate cool air is via evaporative cooling – also know as using a “swamp cooler”. A swamp cooler works by combining warm dry air with water from a tank, producing cool moist output as the moisture evaporates. There are roof mounted and portable swamp coolers you can get for your RV, but they come with a big catch…Swamp coolers only work when the outside humidity is less than 40%, and the dryer it is, the better they work. So a swamp cooler might keep you cool in the desert southwest, but, ironically, it will do nothing but make it feel even steamier if you use one while camped in a swamp.If you’re primarily planning to stick to arid environments, this may be a practical option. If you’re designing for versatility and traveling all over (like us), then this is a lot of space and resources to dedicate to just one climate.
- Ditch The Roof Air: If you want a real AC that can keep you cool on a hot and humid day – you really need to stop pushing a boulder uphill while wearing roller skates. The first step – ditch the boulder – the standard RV roof air.
The most energy efficient cooling capability comes from a modern inverter compressor two-piece “mini split” air conditioning systems, like this 12000BTU Thermocore. But retrofitting this sort of small residential-style unit into an RV is a major engineering undertaking – you need to find both a place for an interior wall mounted blower unit (or two), as well as a ventilated basement area for the outside unit.
You also need to be able to route the coolant hose between these two locations – often easier said than done in an RV.
We’ve seen some RV’s that have been retrofitted with mini split cooling, and they are extremely quiet and energy efficient in operation. We’ve fantasized about a mini split in our bus, but the overhaul that would be required would be prohibitive. We just don’t have any open wall space!
- Cover The Roof With Solar: With no roof AC’s in the way, you can cover a flat roof from corner to corner with solar panels without worrying about shading – maximizing your harvesting capability, even without tilting.
- Deploy A Remote Array: Instead of (or in addition to) covering your roof with solar, park in the shade and set up 1000+ watts of ground-deployed panels at the end of a long extension cable. This will require a substantial amount of setup and teardown, but it will let you optimize your rig for shade and your panels for sun.
- Minimize Your Cool Area: A smaller interior is a lot easier to cool. One option is to just cool the office area during the day, and the bedroom at night.
- Insulate Like Crazy: Insulate your walls and roof as much as possible. Desert buses are actually known for having 6+ inches of roof insulation to help keep the interior cool. Eliminate windows, use awnings to keep the sun out of any you do have, and make sure to use double-pane glass too.
- Go Lithium: Lithium batteries are much more efficient at powering high-current loads than lead, so especially if running an AC overnight is your goal, the advantages of lithium become even more convincing. Make sure you design in enough capacity to keep you cool on cloudy days too.
- DC Air, If You Dare: Converting 12V DC (direct current) power from solar panels or batteries into 120V AC (alternating current) to power the AC (that chill making thing) is an inefficient process. There are however a few air conditioners designed to run directly off of DC power, but few of them work efficiently with 12V power.The reason – transmitting that much 12V power over any substantial distance would require power cables the thickness of your wrist running between your batteries and your AC. As voltage goes up, the cable size required to transmit the same amount of power goes down. At around 48V, DC air conditioning starts to be practical.But using a 48V DC AC means designing your entire battery, solar, inverter, and DC electrical system around 48V – a very unusual configuration for RVs, though common in off-grid homes. Here are two examples of 48V DC mini split systems: Green Energy and Hotspot Energy, and even an RV roof top model by Kingtec Solar.
If you go all out optimizing for off-grid mobile AC, you can do it. And if I was tackling an RV bus conversion from scratch, I probably actually would seriously explore a 48V system and DC air.
I love earning geek points, after all.
But the cost and complexity of retrofitting an existing RV for fully solar-powered cooling just doesn’t make a lot of sense. And if you do go all out building enough solar into your rig to keep cool during a hot summer, you’ll actually have power going to waste much of the rest of the year.
Isn’t it smarter to design for the more typical case?
Roller skates and boulders, after all…
Maybe someday the equations will change, especially if some manufacturer were to apply the technology used in mini split AC units to building an RV roof air.
But seeing as how little RV air conditioners have evolved in the past 40 years, I wouldn’t hold my breath…
Our Setup / Compromise
We did want to be able to run our air conditioner off batteries and get a blast of cold air, or keep the RV cool while in a parking lot while running errands.
In 2011 we started with a 3000w hybrid inverter and 500AH of lithium batteries. This allowed us to be able to run one of our A/Cs off batteries for about 2.5-3 hours before completely draining our batteries. This setup got us through a horrible hot summer when our engine broke down, and we lived in a parking lot for 6-weeks with only a 10A power plugin –we could supplement off battery through the heat of the day, and re-charge overnight. The flexibility of not needing 30A or 50A hook-ups has been very freeing, and given us so many more choices for driveway surfing and better views.
While underway, our only air conditioning is our roof A/Cs, and this setup allows us to run off the batteries while re-charging with our heavy duty alternator (that was originally designed to run the bus’ over the road A/C, which was taken out when our bus was converted to a RV.)
In 2014, we added on 800w of solar on our roof (the max we could install while keeping our sweet vintage looks), and 600w as a ground deployed array. On a perfect sun day, with all of the panels perfectly tilted – we would be able to ‘almost’ keep up with one roof A/C for a short bit of time. But perfect rarely happens, and most of the time we’re not collecting anywhere near enough power to keep up with a roof A/C alone.
When we did a major round of bus renovations in the summer of 2015, this setup allowed us to downscale to a 2500w propane generator. Which is plenty to supplement the energy depletion that solar alone just can’t keep up with.
Other related articles:
Solar:
- Our entire Solar for RVs Series
- Solar Planning: Conducting An RV Electrical Consumption Audit
- Being Electrically Abundant in a Mostly Electric RV
- Our 800 Watt RV Bus Roof Solar Install
- Understanding Solar Panel Specifications
Boondocking:
- Our Entire Boondocking Guide Page
- Being Electrically Abundant in a Mostly Electric RV
- Keeping Warm while Chilly Camping
- Extending the Holding Tanks
- Finding Campgrounds & Boondocking Locations
But What about Gone With the Wynns? – They’re Runing Their A/C off Solar!
In February 2016, our friend’s Nikki & Jason put out a video called Off Grid Solar Powered RV Air Conditioning. Their title is a bit misleading – they are NOT running their A/C entirely off solar (which this article is addressing).
Their setup is very similar to ours. We have 500AH of lithium batteries and 1400w of solar and they have 700AH of lithium and 960w of solar.
They, like us, are running their A/C off batteries, and recharging some of that energy with solar when the sun is out.
Our goal wasn’t to run A/C entirely off solar. But we have been running our A/C off batteries for nearly 5 years, and it works GREAT. We think this is a very practical compromise.
But neither of us has enough solar to keep an A/C running without taking power from our stored power in our batteries. We both will run into all of the challenges listed above. During peak sun, we can keep our A/C going about 3 hours before depleting our batteries. The Wynn’s can get probably an hour or so more with their larger battery bank. But at the end of a particularly warm day – we’re both going to end up with depleted batteries that are unlikely to get us through the evening with our respective electric fridges and certainly not repeating another day of A/C without some sort of alternate re-charge (alternator, generator, electrical plug-in, etc.)
Again, this is cool (sometimes literally) and a very practical approach. But it is NOT running an A/C entirely off solar. So please don’t assume that if you copy their or our system you’re going to be running an A/C all day long, day after day, without ever turning on a generator or plugging in.
Dan Thiels says
the new honeywell swamp coolers are awesome … pulling 220w, i ran the 2nd to largest one on low during the june heatwave ….. never ran the AC at all , used 15 gallons a day and i hooked it to a gravity feed, 65 gallon tank… worth every penny
Chris Dunphy says
In the desert – amazing. Anywhere with a lot of humidity though, you’ll just end up soggy.
Eric Captain Steinback says
Great article, you’re (mostly) right… but I’d like to share that solar-powered air-conditioning a reality, sort of. SolarWOMP has 1250W of Solar Panels and a 10kW Lithium-Ion bank. But even that bank would die in under 6 hours running conventional120vac inverted roof top systems.
SolarWOMP instead has (3) direct 12vdc cooling systems. The first is a rooftop evaporative (swamp) cooler that draws 2-8A/hr. The second is a 3200btu rear-door mounted split system drawing 12-27A/hr. The third is a 6500btu forward roof mounted unit drawing 22-56A/hr.
We use the evaporative cooler as our primary cooling in anything but high humid climates. It does a great job maintaining cabin temperature (and air quality) 24/7 even when we leave the RV parked for the day. We turn the front A/C unit on when hanging out, cooking, etc and turn the rear A/C unit on (and front off) only when sleeping. No it’s not the same thing as running a rooftop unit off a generator… but I have yet to see a Class B with a generator capable of running more than 3 days with an air conditioning load. We have gone 10 days at Burning Man completely comfortable off of nothing but solar power.
https://www.facebook.com/solarwomp/
Chris Dunphy says
You’ve put together a very nice system – an awesome combination of traditional and swamp cooling. Thanks for sharing it!
Allan says
Great blog post! Have you considered using something called a repeat-cycle timer to run the ac a fixed amount of time and off a fixed amount of time in a repeating cycle? For example on for 3 min off for 12 min, or running 12 min per hour? My calculations show that this would result in a comfortable interior climate (especially at night for sleeping, which is what I’m mostly focused on) in my mini van.
My plan is to run a 5000 btu window AC or portable ac on a repeat-cycle timer as indicate above. Using my van ac and mimicking the above cycle seems to be fine for a 80-deg, 60-70% humidity night (the worst condition I’m likely to encounter., since I’m in the west and we typically have low humidity). I plan to have a 150 AH 12V battery bank or 1.8 KW. (possibly lithium). The window ac is 500 watts, and so for a 7 hr night under the repeat cycle it would run a total of 7×12 or 84 min or use 700 watts. Assuming losses it would still be below the 900 watts (50% drawdown).
On a separate note do you know or have knowledge of how to charge a lithium battery bank using the EV charging stations that are quite common and often free around here in the west. Even some national parks have them. The most common is a J1772 plug (240V) that could charge a 1.8 KW Li battery in about 30-45 min given a 3.3 KW inverter. As a reference most EV cars have a 6.6KW inverter that charges 24KW in 4 hrs. using the J1772 plug. Even if you pay for the cost to charge it would be about 30-50 cents on ChargePoint’s network. Others are similar.
Chris Dunphy says
I’ve never seen anyone adapt the high-voltage EV chargers to recharge a 12V or 24V house battery bank – it would be electrically pretty challenging to do. If you do ever run across an example, I’d be curious to hear about it.
LouF says
Great article stating a common dream for solar energy and air conditiong. -Yes, it destroyed the dream, lol.
I found this article while contemplating getting by with a 100W Harbor Freight solar panel and a typical car battery for running my house dehumidifier, I thought RVers would have a similar goal and electric demand. Mine would be in the neighborhood of 525W for 6 hrs. per day, say. – I see it’s not even close. So, thanks to everbody here.
In a crude evaluation a qualitative overview would be: Let’s assume that in order to transform the sun’s energy by counting total losses (inefficiencies) of the system, the inverse of the inefficiencies times the conditioned area would be needed. Therefore, assuming a total 10% efficiency, one would need 10 times the roof area. -Yea, a quick insight to the inpractability (and absolute limit) of the situation within these assumptions.
LouF says
That sounded horrible; here’s a revised paragraph:
A crude evaluation and overview would be: The factor for the solar panel area would be the inverse of the system’s total loses (inefficiencies). Guessing at something like 10% efficiency, one would need 10 times the conditioned area’s roof area.
Jake says
Please allow for alternative thoughts from electronic veteran-hobbyists. There are many many many alternative methods to conventional RV issues. We live around Lubbock, TX with daytime summer temps from 95-110. We sold our roof mount units (Coleman) and replaced with more efficient, quieter window units. Each window unit seems to replace 1 roof-mount unit even though they use only 400-450W each. This means 800-900 total running watts for our entire cooling needs, and keeps the interior at 75 on the HOTTEST of days here. What helped a ton was when we moved from perpendicular to parallel to the suns daily path, parking east to west. This put out broadsides out of direct sunlight and still allowed our panels to shade our roof. Our 1000W seems plenty for our two 5,200BTU window units. Next project is to mount them underneath and connect to our lower floor-level duct system for near silent operation. Cheers!
Cherie Ve Ard says
Window units would make most RVs beyond legal width for highways 🙂 And provide bad aerodynamics, and just in general look horribly tacky on a sweet vintage bus like ours. Not ideal for those of us who are mobile. If you’re stationary, then this becomes an option. But our goal with RVing is to be mobile 🙂
ran says
The issue with using your floor mounted vents is that cold air flows down. Heat flows up, so that’s why (I’m guessing) you had AC units on the roof (so cold flows down) and heaters / vents in the floor (so heat flows upward). I’ve heard that there is a perceivable difference of about 2-3 degrees C over 8 feet in height. So you might do a bunch of work, and realize afterwards that the AC units have to work 10% harder, and tax your batteries a lot more.
I like your idea about parking east / west, but I think that’s not always possible. I’ll try to aim for parking that way more often though.
sandrider68 says
My Aerbus and cargo trailer has 2400 watts of PV (solar) on the 24v system for the Outback Inverter, then another 260 watts PV charging the stock 12v system. LED everything, extra insulation everywhere, Shade to attach and keep the sun off the sides where the awning doesn’t shade the coach, 1000 AH battery, Trojan L-16’s 6v, and I regret deeply not ponying up with a 48v inverter instead of the 24, and using 2v L-16 batteries.
For me to run solar, because I am not there yet by a longshot. Additional 2500 watts of PV, easy enough, to make A-frames that plug in and a string type charge controller so they can just have one wire running through them coming into the coach around 600v, then steps down for charging, this will keep the wire size small enough to use a conventional twist-lock plug to plug them in. Add 12 2v L-16 1150AH batteries. That will do it. Solar has got so cheap, its not the price of the panels anymore. 2500 watts of solar costs about $1100 now. The step down charge controller will be another 600, so still reasonable, and now we will be making about 25 KwH a day. My inverters ‘sells’ so even on metered connections I have a good chance of netting zero. Just don’t tell them what you are doing, just tell them that the solar really helps. My inverter sells when the batteries are full. Or, when I tell it to basically. Outback inverters are infinitely adjustable, so it sells power when I tell it to to keep this simple.
Which leads me to here. This is how you run air conditioning with solar. Using the biggest battery bank in the world, the power company. Install about 5000w with an inverter that sells back your solar power, then you can have a reasonable battery of say 800-1600AH. You can run ac for a few hours when needed, all day in full sun, Good Luck.
Jen says
Hello, I am converting a school bus into a Tiny Home and want to start with a 500watt solar system and I just cant find out if that is reasonable or not. I am only planning on running a small 6ah water pump, laptop and phone charger, 3 LED lights, a plug in cook top, and a fan to begin with. I was planning to run my water heater and fridge off propane (still not sure how this is done) so to me it seemed 500watts was plenty. I am open to adding up to 3 more panels later if there is enough roof space (I have a short bus). Thanks for the help! I have researched tons and I am totally lost when it comes to the electrical!
Cherie Ve Ard says
You’ll want to start with an electric use audit.. and also factor in your battery capacity for drawing loads overnight and on cloudy days. Check our full Solar series at https://www.technomadia.com/solar, we have an audit article there.
Ran says
Two things I would like to mention… My first guess is that 500W is nowhere near enough to run your cooktop, nevermind the rest of your requirements. Why not use propane? Everything else should be fine.
Second thought is that there are a lot of high efficiency refrigerated coolers on the market, drawing not much more than 30W at peak usage. It shouldn’t be a stretch on a 500W system. A lot of people run those fridges on a 100W panel easily. That plus laptop usage, LED lighting (go for “warm light” 2800K lights), chargers, water pump and various low power draw items, should easily be enough for most days on a 500W. Anything relating to heat / cooking, propane is usually the way to go.
Scott Bennett says
Yep, a propane tank fueling the stove along with the water heater if you cook a lot, a camp stove if you don’t.
ran says
I wasn’t aware but a lot of people are running induction cooktops that (when using the right pots / pans) heat the pot or pan directly, preventing most of the loss of ambient heat. I heard that a typical electric stove will be 50% efficient, whereas an induction cooktop or even an electric kettle is closer to 90% efficiency. With the kettle, I’ve seen figures of 1200Wh in use, and depending on how much water you boil, say for 2 minutes of use, you’re looking at only 40W. On the other hand, drawing that much juice could be bad for the system.
Cherie Ve Ard says
We run only induction in our RV for stovetop. Lithium is great for this, as it can handle high draws.
creeky says
http://www.hotspotenergy.com/DC-air-conditioner/
The list of comments is so long I didn’t see if anyone else had posted this already.
But there are a variety of DC powered a/c heat units now. This one is particularly interesting as they say it will run off 1000w solar panels. and can be configured to use batteries with 135ah/12v being enough for 5 hours of night use. They have nicely configured the system as well.
Be interested in your thoughts.
I use a 5k btu window unit at my camp. I am off grid solar on year 7. Last July I installed a chevy volt based lithium battery. Wow. What a nice upgrade on my lead acid pack.
My blog if you’re interested is at creektreat.ca
Cheers, Creeky
PS-hi Reed.
Chris Dunphy says
That is a neat looking system – but as I wrote about, a 48V mini-split DC AC would be nearly impossible to retrofit into most RVs.
But if you were doing a shell-up conversion, this would definitely be something worth checking out.
Cheers!
– Chris
ran says
You probably know a lot more than I do about this, but wouldn’t it be fairly straightforward if you just installed a dedicated 48V battery to feed only the AC while charging it from the existing PV system (perhaps adding more panels as needed)?
ran says
Woah, cool (pun intended). So it requires 800 Wh at peak operation. If you have a 1000Wh Li-ion battery system, or 1600Wh lead acid batteries, that should be enough for the hour. Of course you wouldn’t be running at peak operation the whole night, but I’m wondering how they figured 5 hours without really knowing the conditions, the windows you have, the insulation, the ambient temperature, consumption from other devices, etc. According to their chart, at “normal” usage, you’re still burning through 450Wh.
Dave Winters says
I have searched and researched this topic for a very long time in order to properly build my set-up. I just finished reading all 3 of your chapters.. And you guys have opened Pandora’s box with me with your wealth of informative and intellectual properties on this issue. I have many electrical diagrams and drawings of what I was hoping to do with my rig. But now with your help I have truly had to update my plans. Lol. Really hit the nail on the head with me and I just have to say thank you so very much. Love You Guys. Take care and stay safe out there. PS, also watch all your Youtube Blogs as well. Ciao
Kathryn Johnson says
Yea, small window ac’s can use much less wattage. My 5000 btu works great as a room ac and uses 500W. Like the article stated, your biggest issue will be the battery bank. You need enough amp hours to be effective, and enough solar power to recharge the batteries. This is where trouble comes bc a battery bank large enough to run your ac without discharging over 50%, takes at least a day of full sun to recharge.
To calculate how many hours it will take to recharge your batteries, convert your total battery amp hours into watt hours, then divide by your total solar wattage and multiply by 2 (this number alots for less than full sun, resistance in the system and energy loss, etc)
Calculate the total additive amp hours from all batteries connected in parallel (not series), and multiply by the voltage (non additive if in parallel). The voltage is 12v for factory rv set ups.
So say you have a total of 2000 AH lead 12V battery for all batteries, and 1500W solar power. The formula is 2000 amph Á— 12V = 24000 watt hours for all batteries combined. Now take 24000 W battery power Á· 1500W solar power = 16 hours Á— 2 = 32 hours to fully recharge. Assuming you depleted them to 50% then it would take 1/2 that time, or 16 hours. If you depleted them to 60% then take 100% – 60% = 40%, and the time is 32hours x 0.4 = 8 hours to recharge.
It is simply not feasible to run a 120V AC off strictly solar power except to cool off in emergencies. The batteries would be too many and too heavy, and the solar power take up too much space, HOWEVER…if you are not mobile, and have a permanent place and enough money, then with a 20 count battery bank housing area and enough ground area to put about 30 100W or eight, 400W panels, it can be easily done with the right controllers, inverters, and cables.
Rand says
This is the 2nd dream you killed for me. 😉 This and satellite internet being unavailable for those of us who want to move around. Anyways, I was wondering if you guys think any of these additional alternatives could help with heat management, either in addition to AC, or without…
1) reflective paint on the roof, assuming that the rooftop is not metallic (like your bus). This seems like a no brainer.
2) given that heat rises, rooftop venting fans should help that heat escape efficiently.
3) floor mounted fans to bring in cool air from the shaded underside of the bus (on the side of the awning). This may be your only shade in some areas. If those don’t exist, or you’re not earning enough geek points to rig something up yourself, at least a floor vent (read: hole) could increase colder air flow.
4) More fans. Reducing the perceivable temperature a few degrees lower is probably all that one could hope for without being hooked up to shore power.
5) Understanding your environment. You guys alluded to traveling north or heading up to mountains, I would just like to add that coastal areas are generally more moderate, both in summer and winter conditions. Here in the PNW we don’t get much higher than 32-34C and that’s usually no more than a month in the summers. Also, it very rarely snows in Vancouver, BC anymore. But you have to put up with the rain.
6) A solar / wind hybrid setup that would allow you to generate juice at night. The thinking with that is that if your conditions are good (ie. in coastal environments) but you’re worried about battery depletion, the wind turbine could at least power your fridge and lights. In theory it could get you a little cooler during the day because you would be less worried about draining your juice at night.
Thanks for all of your dedication to the subject, it’s very much appreciated. Here’s hoping solar efficiency and AC units will improve in the coming years.
Cherie Ve Ard says
Hi Rand… actually, there are two satellite internet options that are mobile. Check out our overview article at http://www.rvmobileinternet.com/overview
And indeed, there are more ways than air conditioning to keep cool. Air flow definitely helps, and sometimes is all you need.
We’re not personal fans of wind turbines – at least on our RV, as 1) they’re usually pretty difficult to setup/stow (unless you get really fancy) 2) not many environments folks RV in are suitable for wind power and 3) the noise.
Randy says
Yeah a bit of a long shot but thought it might be worthy of some geek points.
One other thing I forgot to mention in terms of heat management would be a natural latex mattress that is super breathable along with pure cotton sheets (no polyester at all). That’s my mattress plan, in addition to a nice memory foam mattress topper for winter climates. All those foam and polyester products really insulate the body heat.
Zarius says
So, hey, I’d just like it if you could check my math on this because, while I have a basic founding in electronics, I’m not an electrical engineer, and so I’m not 100%.
This AC unit:
https://www.nationalequipmentparts.com/collections/gree/products/gree-crown09hp230v1ah-mini-split-indoor-unit-9k-btu
Has a max power input of 1400w. If my math is right, that means that it runs at 1.4 kw/hr if it’s running full tilt for an hour.
These panels:
http://www.costco.com/Grape-Solar-100-Watt-Polycrystalline-PV-Solar-Panel.product.100054656.html
Have a max output of 100w per hour, so 20 should run the AC without a problem.
If my RV/camper has an exterior dimension of 28′ L x 7.5′ W, then those panels should fit 2 high, and more than 10 wide.
And a 9,000 BTU AC is rated for up to double the space of the camper, so as long as the STOVE isn’t on, this SHOULD work with some room to spare, correct?
Chris Dunphy says
It should work pretty well – assuming that you can tilt the panels towards the sun, and only need AC during the heat of the day and not overnight.
Do remember that a 100W solar panel will typically be putting out a lot less than a full 100W of power. In general, it is only capable of full power when it is aimed directly at the sun.
Even a bit of shade or haze can drop the output a ton.
But if you do manage to get 2000W of solar onto your RV, I expect you’ll be able to get a nice amount of AC run time per day.
Cheers,
– Chris
Don says
Hi guys love your videos my wife and I will be nomads soon as we sell our home. The information you and other nomads provide have given me insight to the lifestyle and we still want it even with the sucky side. Because big city life is no longer an option we are burnt-out. Thanks again can’t wait for the next chapter of your experience which is very helpful to us newbies. Oh and we will keep wine on hand in case we bump campers in the night:)
Richard Bateman says
I’ve recently been working on a similar problem; I recently picked up a window-mount (normal house window-mount) 8000 btu air conditioner which turns out to keep my trailer fairly reasonable in all but the absolute worst temperatures. I keep it in the back of the truck, then put it in when I need to use it. I accidentally ran it off of my batteries for a good half day before I realized (because the batteries were getting low) that I was running it off of the battery and not the external power.
Based on that experience and that the 8K btu AC is only rated at 700 watts I’m going to try upping the solar panels on my trailer from 512 watts to 1.2K watts and I think I’ll be able to run it decently.
Just sharing another possibility =] Given that heat rises and the extreme heat on the roof, a window mount air conditioner which you can get for $300 from a hardware store may actually do a much better job — particularly if you have a couple of options as to which window to use and can put it on the side in the shade. Granted, this won’t work for everyone — my trailer is a custom conversion from a toy hauler and has a bit more battery and a bit more panels than most.
Kathryn Johnson says
Yea, small window ac’s can use much less wattage. My 5000 btu works great as a room ac and uses 500W. Like the article stated, your biggest issue will be the battery bank. You need enough amp hours to be effective, and enough solar power to recharge the batteries. This is where trouble comes bc a battery bank large enough to run your ac without discharging over 50%, takes at least a day of full sun to recharge.
To calculate how many hours it will take to recharge your batteries, convert your total battery amp hours into watt hours, then divide by your total solar wattage and multiply by 2 (this number alots for less than full sun, resistance in the system and energy loss, etc)
Calculate the total additive amp hours from all batteries connected in parallel (not series), and multiply by the voltage (non additive if in parallel). The voltage is 12v for factory rv set ups.
So say you have a total of 2000 AH lead 12V battery for all batteries, and 1500W solar power. The formula is 2000 amph Á— 12V = 24000 watt hours for all batteries combined. Now take 24000 W battery power Á· 1500W solar power = 16 hours Á— 2 = 32 hours to fully recharge. Assuming you depleted them to 50% then it would take 1/2 that time, or 16 hours. If you depleted them to 60% then take 100% — 60% = 40%, and the time is 32hours x 0.4 = 8 hours to recharge.
It is simply not feasible to run a 120V AC off strictly solar power except to cool off in emergencies. The batteries would be too many and too heavy, and the solar power take up too much space, HOWEVER…if you are not mobile, and have a permanent place, then a 20 battery bank housing area and enough ground area to put about 30 100W or eight, 400W panels, it can be easily done with the right controllers, inverters, and cables.
Mark says
Very informative, thank you. I hope to do extended traveling with my dog and anticipate needing to leave him for up to four hours in a motor home, trailer, or camper in warm climates. Obviously, I would only do that if I could safely and reliably cool the compartment while the dog is left there. I’ve learned of techniques to monitor the temperature remotely, so that helps. Do you have thoughts or leads on equipment to cool a mobile compartment like this with passive solar? Other ideas? I suspect this has a market but I couldn’t find find anything reliable and controllable to fit this need on the internet. Thanks!
Cherie Ve Ard says
All of our alternative ideas were shared in the article.
Brandon says
I’m wondering if you could compensate for the battery drain (with an a/c powered by a good solar system) by connecting it to the alternator and driving around a bit each day? Not to run the a/c constantly, but just enough to make it more comfortable?
Cherie Ve Ard says
We do have our alternator setup to charge our batteries while underway. We do this mainly because the only AC we have on our bus is the roof airs (no dash) and this allows us to run the front AC while driving. If we have a choice between dry camping in the heat, or getting miles in to our next destination… it’s an obvious choice which is more comfortable 🙂
As far as just driving around aimlessly to top up the batteries, it’s better for us at that point to just run the generator. Fuels costs are less, no packing up to get the bus ready for ‘motion mode’, no risk of traffic/accidents, we can get work done, etc. Besides, it would still be hot out, and we’d want the AC running while doing that driving, which wouldn’t result in topping up the batteries all that much.
Jacob says
Stacking solar cells on a tractable system might be one way to add more cells to the roof. Has anyone thought about building a retractable solar array on their roof? Is this possible?
I drew a proof of concept:
https://s32.postimg.org/izffbd9ut/RV_Roof_with_Retractable_Solar_Array.png
Jacob Morris says
There’s another solution I never really here people talking about…retractable, roof mounted solar array.
I drew an example of what I’m talking about:
http://postimg.org/image/hotvutqob/
What if you were to build an electric, roof mounted track that would allow you to stack solar cells two or three cells deep that expand and collapse in and out.
While your in motion, you’d have them collapsed and stacked, but once you get to your destination you expand the array automatically out like a fan.
I would think this could potentially give you enough or close to enough power in some cases with full sunlight.
Jacob
Chris Dunphy says
A system like that would be awesome indeed – but it introduces a LOT of mechanical engineering complexity, especially since it will need to be able to withstand windstorms.
If anyone were to ever build something like this, they would get mega-cool-geek points – and I would love to see it.
But I think it would be very hard to commercialize a setup like this in a cost-effective and easy-to-use fashion.
Cheers,
– Chris
Hannah says
I’m wondering if a super-efficient mini split ac with inverter would do the trick. This one seems to require really low wattage in comparison: http://cooperandhunter.us/wp-content/uploads/2015/06/GWH12QC-D3DNA1D_small.pdf but it has zero reviews on Amazon – any ideas how to calculate what kind of solar setup this would need? I just bought an RV days ago and am a total n00b in this department 🙂
Chris Dunphy says
It looks like Cooper & Hunter makes some very nice Mini Split systems. Their 120V model uses around 1000W when cooling, which would still require a pretty hefty solar system to keep powered. But this seems like a great place to start.
– Chris
MICHAEL says
Awesome Chris, love your stuff. Tons of useful info for those of us considering that huge project.
Allen Tompkins says
12,000 BTU DC Air Conditioner For Off-Grid Solar & Telecom Applications
http://www.hotspotenergy.com/DC-air-conditioner/
Chris Dunphy says
That looks like an interesting unit. But I do note that they call for 2500W of solar and 16 gold cart batteries if you need 24hr air conditioning, and you also need a 48V DC system. And that is for a 12,000 btu air conditioner that has less cooling capability than most typical RV AC roof units.
– Chris
Travelingamericas says
We have running our camper AC all from solar. We have 600W of panels and 660ampH of AGM batteries. Aircon is new Dometic Freshjet 1100 and it consumes about 33amps of power on 12V. That Donetic AC works on 230V and we have a inverter what makes 230V from 12V. Our camper is 9m2 and we can safely run our AC 8-10 hours of the night and wont drain the batteries over 50-60% of the capp.
System is tested out in almoust 40celsius and it works. But there is a catch. We run our AC only at night time and let the batteries charge back to 100% during day time. If we beed cool breeze at day time we have huge 230V fan what makes you hold on something if you walk past it 🙂
Our Instagram account is: travelingamericas
If anybody is interested to see what kind of camper we have
Chris Dunphy says
That Dometic Freshjet is a European 230V model that is 1/3rd the power consumption and cooling capacity of the smallest Dometic roof air available in the US compatible with US voltages.
But for a small custom rig like yours – it seems like a perfect match.
Looks like you guys are off on a great adventure with an awesome rig – cheers!
– Chris
Jason Wynn says
Noticed your addition linking to our website while doing a google search. You are 100% correct that we are not running our A/C off solar (that title references the number one question we get about solar) As for the amount of hours we can run the A/C: We feel running the A/C during full sun will get us cool air for 4-5 hours and leave us with a battery bank around 80%. Based on our previous testing going to bed with a battery bank at 80% means waking up around 70%. A few hours of solid sun in the morning and we’d be back near 100% around lunch. Of course this is all “in theory” since we haven’t tested it.
I enjoyed reading the article.
Leon Weenink says
Hi,
I’ve been looking into the same and came across Red Dot A/C (12/24V). They suggest their larger units use around 30amp (@12v) for 25000BTU cooling.
http://www.cabairconditioning.com/rd1.html
What do you think?
Leon
Chris Dunphy says
I’ve never heard of Red Dot, or seen a unit like this used in an RV.
Their claim of 25,000btu cooling capacity drawing just 400W power does seem overly optimistic, but if they can pull it off and someone has first hand experience, I’d love to hear about it.
Cheers,
– Chris
Andreas says
A lot (all?) of Red Dot’s units have only the converter or converter/evaporator, not the compressor (chiller), which is the most energy-intensive component of an a/c system.
Joe says
It’s already been done, and without all the hoopola you made it out to be. https://youtu.be/B0rZY5uotKI
Cherie Ve Ard says
Yes, the Wynn’s, just like us – can run their A/C off their batteries and supplement those batteries with solar. But this is NOT the same as running an A/C entirely off solar (which this article is about – and was published a full year before the Wynn’s put out their video – heck, it was published even before they got this RV setup). They are running at a deficit.
We have a very similar setup to the Wynn’s (we have 1400w of solar and 500AH of lithium, to their 960w of solar and 700AH of lithium).. and have been running A/C off battery for nearly 5 years now with this setup.
That means they can run their AC about an hour longer than us entirely off battery, but we can charge up a bit faster during peak sun. But even so, after a long day of running the A/C, we and they, would need to re-charge somehow. And neither of us would be able to run an A/C overnight entirely off battery.
Leon Weenink says
Hi,
Just want to know, is your 500AH system 12V, 24V or 48V. Makes a hudge difference in energy stored and also changes the equation for storing and extracting due to loss. Is it the same as the 700AH system?
Cherie Ve Ard says
Ours is 500AH at 12v. More on our system: https://www.technomadia.com/lithium
Mark says
Great article covering all aspects of DC air condition! After seeing the Wynns video on their experiment with DC air conditioning, I started thinking how nice it would be have a similar setup.
Cory Davidson says
I found this blog because I am searching ways to use solar power and have a roof AC, in the semi sleeper I’m building. Access to grid electricity or shade is not an option, usually, um, ever, so I need to be able to stay cool with the least amount of diesel / motor wear as possible. Your article was fun and informative, but do you have any ideas on what l I could adapt, or most efficient way to do the AC? I have 4 12v truck batteries and will be using an inverter for outlets and fridge, etc. The sleeper will be set up for shore power, but that will rarely be available. Any tips would be greatly appreciated!
Cherie Ve Ard says
Hi Cory – Chris listed all of the ideas he had for implementing solar powered AC in the article above.
George says
Fantastic write up! I really appreciate the time and thought you had to have put into this. I was one of those many emails that you had regarding this topic. Your comments about the mini-split a/c system intrigued me, so I did some research on them. From the things I’ve read, and an Architect friend has a similar opinion, these systems are very efficient, very quiet and generally are a good quality purchase if the need warrants one (no different than what you said in your blog).
I have a 37′ 5th Wheel with 4 slides. I have two roof mounted RV A/Cs – ducted. One 15k BtU and one 13.5k – 28.5k BTU total. As I was researching split systems, I asked myself, how many BTUs do I really need to cool the 350-400 square feet of my RV. According to conventional calculations for household systems, a 5000 BTU unit ought to be sufficient for 400 SqFt. That really has me perplexed. Why does my RV have so much more? I figure there are three things that affect this: 1) RVs are very poorly insulated when compared to today’s houses. 2) RV a/c’s themselves are not very efficient or effective, when compared to a ducted house a/c system and 3) air circulation. These are probably three reasons why an RV needs more cooling power than a home. I’m sure there may be more reasons.
I figure that I’m going to have to replace my a/c’s eventually, why not replace them both with a dual zone mini split system, which will give me nearly the entire RV roof top for solar panels.
So, here’s a question related to air conditioning systems. I apologize for putting this in a solar related blog, but this is where you talked about the split system.
If I were to convert to a mini split will I be able to use a 1ton (the smallest available) to cool my RV? Are they really that much more effective than conventional roof top RV systems? Or, is there another BTU calculator that I should be using for determining the proper size ac for an RV?
FYI…Some mini split systems also offer ceiling mounted inside units.
Cherie Ve Ard says
Afraid we haven’t delved too deeply into the details of mini-splits, as they weren’t a practical option for us. But the benefits seem worthwhile if it’s an option for you.
Gary Matta says
STOP! yes you all make good sense. But nobody is talking about FREON. The new R410 freon is substantially more efficient, and most new split systems are now R410. Please consider the coolant/age of each a/c unit when you are discussing apples and oranges. Or r410 split house units and r162 standard /anything over 4 years old, 12v systems. even the new home window units now come with the r410. Only downside is r410 operates at a much higher pressure, professionals should be consulted.
Colin says
Enjoyed your article and I’m sure it applies to many. I have a small teardrop style camper, a 15 foot by 6ft T@B to be more precise (Google it). Many come equipped with a small window type AC unit like you can buy at WalMart for a $100. The T@B has a considerably smaller area to heat and/or cool than the big rigs you are use to. Many of us use from 200 watt panels down to 100 watt to keep the batts charged if dry camping. Also many T@B boondockers install the dual 6volt series linked golf cart batts (ie. Trojan 105) for the extra reserve amps. From what I read on our forum at Little Guy, most consider Air Conditioning a thing reserved for shore power time only. Some claim their 1000 watt Honda generators will work. Like you say, solar for now is pretty much a fantasy especially in hot high humidity environs. Good advice you give to follow the low humidity with lower temps around the country.
Cherie Ve Ard says
We actually full timed for our first year in a T@b back in 2006 & 2007. Equipped it with solar and 2 6v batteries, and left the A/C off so we had more storage room. Fun little trailer.. and fun memories! And we did nearly a year entirely off-grid with that set up.
Andrew says
Hey Technomads! I had a question regarding ac for a small van camper conversion. I am in the R/D stages and am looking for the best components for stealth camping and such. I was curious what your thoughts were on cab ac units used for Semi trucks such as these units made by Dometic: http://goo.gl/j3RT8c (the link was 500miles long so I shortened it). Now as far as btu’s go I’m leaning towards smaller output because of the small sq ftage I’ll be needing to cool.
Chris Dunphy says
Those cab coolers could be the foundation of a great system – but they are still HUGE power hogs, relative to most other loads. It will be hard to fit enough solar onto a small van to keep one going for more than an hour or two per day.
But if you have a big enough battery bank and charge while driving every day or so, you could probably make this sort of setup work.
Good luck!
– Chris
Gary Matta says
most people don’t realize that even a van a/c compressor pulls 8 Horsepower, not amps, from the engine, just so much built up heat and to cool it down in 10 minutes takes a lot of btus. 30,000 or more, that much will keep a small house cool.
Zach B says
First of all, Thank you two for doing this. The whole thing — RV life, lithium batteries, solar arrays, wireless communication and blogging about it all. I bought a Class B 2 years ago with the intention of doing all of these things to my rig, and am supremely happy there are awesome folks like you out there blazing trails and informing newbs like myself about it!
Per your 3.5 year lithium update, I’m going to be talking to one of those fine installers about putting a lithium/solar system in my RV, but the A/C situation has me stumped. I plan on eliminating my generator and propane, since I don’t use a microwave, fridge can run off electric, and will replace my gas stove and my gas furnace/heater with electric ones.
As such, do you think it is feasible for a 300AH battery bank with a 100W solar charger to run a 7100BTU a/c for a few hours a day while running a fridge all day, laptop a few hours a day, and a few small USB items?
One 100W panel on the roof is all I have the space in/on my van for (certainly not any deployable arrays), so I’m curious to know if that would do much to reduce battery depletion while running a high-impact appliance.
One little thing, which may or may not affect the efficiency of my potential situation is that the camper top on my RV is that the front dips down on the back about 7 inches (i.e. taller in the front, shorter in the rear –search “dearborn class b rv” and you’ll see what I mean), and the a/c is on the rear of the van and the solar panel would go in the front up top.
Sorry if I sound completely ignorant, but I basically am. :-/
Chris Dunphy says
You are going to need a LOT more power to be able to do even a fraction of what you want. You’ll probably have trouble even keeping up with your laptop with a single 100W panel.
If your fridge is dual-mode propane and electric, it will use a ridiculous amount of electric power to run. That style of fridge is incredibly efficient with propane, but is horribly inefficient with electricity. If you really do want to go electric only, replacing your fridge will be your first step.
Propane is a great energy source for making things cold or making things hot – what is your reason for getting rid of it? If you do want to go down this patch, you will need a lot more than 100W, and even then air conditioning and heat will be hard to sustain.
Good luck, and keep reading! You’ll get a handle on this stuff eventually – just take your time.
– Chris
Norman H says
Have recently seen and felt this unit in-use in a demonstration setup with 1200 watts of curved solar panels rooftop.
http://us.bergstrominc.com/nite-phoenix/
This is designed for truckers to lower idle durations. Seems to be a pretty nice product. Not sure how easy it might be to fit it into an existing rig though.
Chris Dunphy says
That looks pretty nifty, and there are indeed a lot of truck-cab systems out there.
The challenge is finding a way to integrate these designs into an RV. And most RV’s have a lot more interior space to cool than a truck sleeper cab too.
But certainly an interesting avenue for exploration.
– Chris
Reed and Elaine says
Great article and comments on the thread.Learned a lot from the comments on the thread
As you note “…At around 48V, DC air conditioning starts to be practical…” Since we already have a 48 V (nominal) LFP battery suite, we have looked into replacing it with a mini-split level a/c.This would also lower the structure on the roof and we could place another 470 W on the roof. That space is now in shadow from the a/c and cover.
Not sure we agree with statement
“…But the cost and complexity of retrofitting an existing RV for fully solar-powered cooling just doesn’t make a lot of sense. And if you do go all out building enough solar into your rig to keep cool during a hot summer, you’ll actually have power going to waste much of the rest of the year…”
With 1420 W of solar, we run the Dometic fridge 24 hours on days with high insolation. We also run the hot water on solar during the day. The Dometic a/c takes about 1750 W and we can collect up to 1400 W on a day of high insolation so we have run the a/c for 3.5 hours a number of times. We have been harvesting up to 8.5 kW-hrs recently in mountains of northern NM. A mini-split level with equivalent cooling would be approximately 800 to 900 and we could run it all day.However, our modus operandi is “Goldilocking” as in go “where it is not to hot and not to cold, just right” We go north and/or up in elevation when it gets hot and reverse when it gets cold. This is easily done in Rocky Mountains of NM, Colorado and Wyoming.
Reed and Elaine
Chris Dunphy says
You guys seem to be doing it exactly right – finding a balance point between moving to find temperate climates, optimizing solar, and being conservative in your AC usage. It can be done, clearly, it just takes carefully managed expectations.
Replacing a roof unit with a mini-split will be a challenge – but an exciting one. I look forward to hearing how well it works out for you, and what products you choose.
Cheers!
– Chris
Tim says
We aren’t thinking we can power our ac by solar.. We have a generator. However, while driving down the road, what’s the thought on running ac on battery an hour before or destination?
We have +400AH in batteries, and 480w solar on the roof.. 3000 inverter.
The idea is the unit would be cool when we arrive and crank up the generator to take over.
Some have told us don’t run ac on batteries..
What do you say?
Chris Dunphy says
If you have a quality pure sine inverter, and you are careful not to drain your batteries too low, you can probably do a pre-chill cycle the final hour before arrival and firing up the generator. This is actually a smart pan.
But make sure that your system is optimized to handle the load – and if you are using lead batteries, make sure you have a real battery monitor and never let them get below 50%. At first sticking to 30 minute runtimes might be smart too until you learn to trust the system.
Cheers,
– Chris
Quintus Aucamp says
Thank you Chris!
I have been searching for info on this topic for years now. Your explanations, reccomendations and insight is absolutely priceless. I live in a park in Phoenix and due to my work situation can’t just move up to the mountains.
I recently installed a TurboKool. I find it to be ‘somewhat effective’. For instance, right now outside temp is 107 with humidity at 9%. Inside is 96F with 22% humidity. I have 37′ coach, but close off the bedroom and bathroom during the day.
I’m parked in direct sun and have outside UV window coverings, inside curtains and day/night blinds and window awnings.
I measured the Turbokool (which only draws 7.5 Amps) output right at the vent and at this outside temp it was outputting 92F.
What I do now is when I get back from work, I can fire up the Ac’s and it cools down the coach much quicker.
As you stated, this would obviously not be a solution when humidity rises above 40%.
Thanks again for your insightful article!
Chris Dunphy says
Out in the desert a swamp cooler like the TurboKool can indeed be extremely useful. Thanks for sharing your experience!
– Chris
Gary says
Chris take a look at the Magnum Hybrid Inverter. Worked great in my Airstream using a single Honda 2000. It mixes battery, solar and shore power together. It is 3000W and did a fine job. Still can’t run 24 hours but certainly for several hours in something the size of an AS. Maybe not so good in the bus 🙂
Cherie Ve Ard says
We too have a 3000w hybrid/booster inverter (by Victron)… but for the purposes of this article, resorting to using a generator doesn’t count 🙂 That’s not to say it can’t be done, but that’s not running entirely off solar.
Rochelle says
I was referred to your article by a fellow small-camping-trailer owner. Our units are 4×8 with 48″ floor-to-ceiling, with 5000BTU a/c units installed in the upper front wall above the tongue. Our Facebook owners’ group currently has a discussion going about the possibility of using solar for our small trailers. Since we don’t have big rigs with big a/c, what do you think of solar for our application? Our camping trailers are similar to teardrops but not the teardrop shape (front and back are equal with a slightly curved roofline). They are pretty much shells that we furnish and outfit ourselves (for reference: Runaway campers dot com). Thanks for your opinion and input.
Cherie Ve Ard says
All the same principles would apply.. small or large. While you have less space to cool, you also have less space for solar, batteries and inverter. On our 17′ travel trailer, if we removed all other roof gear (A/C, fan, antennas) – at most we would have been able to get maybe 300-400w up there, and only had room for about 240AH of batteries. Not enough to power even a small A/C.. we always had to us a small generator for it. On our T@b teardrop, we could only get 120w – again – just enough for lights and computers.
So, just like any other setup – you have to design for it and think it through, and make compromises.
rich hahn says
I’m planning on doing some experimenting with shade cloth to see if I can keep the rv from getting so hot in the summer. The vendor said he didn’t think there needed to be an air gap to be effective, so I’m thinking of cutting out holes where the solar panels are.
ScubaShan says
When we designed our expedition truck we did so with 100% reliance on solar power for heating, cooling, and cooking. The 1200W of LG Neon panels are ~110mm off the top of the camper which forms a nice tropical roof so we’re always “in the shade” even when parked in the sun. The floor, walls, and roof are 35mm polyurethane foam/FRP composite panels which have an R value double that of the standard eXpanded PolyStyrene (XPS) . The windows are all double pane insulated to further reduce the transfer of heat.
The AC is a Mitsubishi Heavy Industries 2kw inverter split system that has an EER of 5.9 , so the draw on full power is just 350W. As its an inverter model with a variable compressor its able to both reduce the draw to just 170W, as well as increase its heat pumping output to 3kw (drawing ~550W) to quickly reduce the temperature in the camper when required.
Over summer in Brisbane (Australia) we averaged under 200W even on days where the outside temps exceeded 36c, which was well within the capabilities of our solar and lithium batteries. Its a little less efficient at heating so it’ll be interesting to see how it handles winter when we travel to cooler climates to do some skiing.
One idea we are toying with is installing some sort of heat exchanger under the panels to pump glycol through our HWS which has a 240v electric element and also a hydronic element that would usually be plumbed into the engine coolant system. This should increase the solar output by lowering the panel temperature and lower our electrical load by reducing the power consumed by the HWS.
Chris Dunphy says
That is an awesome setup you have!
I’ve also been fascinated by the possibility of combining a solar water heating loop under the roof panels. For our current rig the plumbing required may be too complicated – but if I were designing a solar rig from scratch that would be an awesome way to go.
– Chris
James D. says
This is known as Solar Thermal roofing… Companies like Dawn Solar Systems do this professionally for residential homes…
It is done much like how a radiant floor system is installed, and the metal roof goes over it and then finally you can add solar panels.
Solar thermal can be combine with a heat exchanger so the heat taken off the roof can be used for something else, like heating your hot water, which in the winter time can be used with a radiant floor system to heat provide heat through the floors, or you could reverse it to melt snow and ice off the roof…
So this has multiple benefits… It helps keep the solar panels from over heating, it draws heat off the roof which reduces your solar gain and thus helps keep the interior cooler, and lets you turn that heat energy into a useful application.
Small vehicle mounted wind turbine could provide enough power to power the pump for the solar thermal system as well while driving…
For Mini-Splits, besides the standard wall units, there’s also ceiling and in-wall units. You can also install the unit in a utility closet and then duct it to where you need it.
So you could simply mount the compressor on the rear and you can put box it if you don’t want it visible, run the lines right through that rear wall and then duct the interior unit through the bus… Or, if it’s a diesel, then just use one of the storage compartments below, vent the door and set it up from there just like you would a central vac…
There are RV split systems that mount the compressor underneath but that has the issue of exposing it to all the dust, dirt, and other particles as the vehicle is driven around, which can quickly dirty the unit and make it operate less efficiently.
richard addy says
This issue that [glass] panels produce interior heat to an RV; I always thought that these same panels would aid in interior cooling by the shade they would produce to the roof, esp with the open gap in between, What if gap was increased, would it go the other way?. Thanks for the heads up on this, it helped.
John says
You’re right. My 35 foot MH is almost completely covered with 8 230 watt aluminum framed glass panels. They all have 4-6 inch spacing and are 1 – 2 inches off the surface. With this and the tinted windows I easily cool the inside on a 100 degree Utah day with my 9000 BTU mini split which uses only 800 watts on high.
Chris Dunphy says
Indeed – with enough of a gap to allow ventilation, raised rigid panels actually can provide some shade. With thin and flexible panels glued directly to the roof, not only is there no shade – but all the heat build up is transmitted directly to the interior.
This ended up being one of the key reasons we went with glass panels instead of thin.
– Chris
Gene Failmezger says
Intriguing article, Chris. I saw a split AC system in a Class A once at a camping world. Only once. Ha. I imagine that it would definitely be quieter. It was a residential unit. I bet no one could work on it and I bet it was also not very reliable (due to the rigors of road use).
I work for an independent phone company. Our primary power is -48VDC. (why the neg, I will never know, but it is they way it has always been done.) This said because there is a lot of equipment designed for 48VDC. We have banks and banks of Exeltec pure sin wave inverters powering all sorts of things that require AC. I so my damnest to find anything DC powered I can though. All our routers and servers are -48VDC powered directly.
Gene Failmezger
Sumter, SC
Video Engineer
FTC, Inc.
John says
My 9000 BTU mini split, with the condenser mounted on the back of the MH has 3 years and 20000 miles with no issues. Cooling is excellent. I don’t miss the (2) 15000 BTU 2000 watt electricity hogs that were mounted on the roof. A roof mounted array of (8) 230 watt panels provides plenty of power.
Rob Nixon says
Great article, Chris. I have a friend who runs his house (including AC) and business off-grid on solar power. Your analysis is right on.
This discussion could get a lot more interesting when the new Tesla battery factory now under construction gets into production. I’m thinking RVers could do a LOT with an 85 kWh battery similar to the one now used in the Tesla Model S. Expensive, no doubt, but with tons of potential for boondocking RVers.
John says
I have too many split systems on MCI 7 since 2006 and they will drop the temperature to 60 degrees in Tucson in the summer time electric bill will run about 80 to 90 dollars
sushidog says
Super article! Thanks. I’ve been planning a 12k BTU 48v (560 watt draw – only 11.5 amps at 48v) minisplit heatpump system for about a year now to go on a travel trailer for FT use. I probably won’t buy it for a few years which will allow battery technology to advance a little. As it stands, I’ll probably start with a learner bank of 8, GC-2s (golf cart cart batteries) and graduate to far superior lithiums when they expire. This will help my cash flow, lessening start-up costs. I considered heat load and am envisioning a blanket of large high voltage grid tie solar panels, possibly rack mounted – of around 2,000 watts. If I mounted them flush with the top of my single retained roof AC unit that would allow sufficient airflow underneath to dissipate most of the accumulated heat. Plus if boondocking in the desert (where there is no shade) I’ve brought along my own shade. 😉
To your issue of wasted solar capacity when no air conditioning is required, the heat pump I plan on using is a very efficient heater in milder weather too, consuming 600 watts of power to make 12,500 BTUs of heat. This will spare propane usage in winter too, allowing for longer boondocking forays.
Of course 12,000 BTUs won’t be sufficient to cool the entire trailer at peak summer daytime heat, it will extend by boondocking season by a couple months. I plan to mount the inside air handler on a bedroom wall, ideally blowing down the bathroom hall. I can then close the bedroom door using less energy to obtain a cool, peaceful nights sleep. Also cooling at night will mean a lower duty cycle too.
It may sound like an expensive proposition at first, but I can put a system together today for around $5-6k (with the cheaper battery bank.) If one considers the money saved on monthly campground/rv park fees and metered electric (about $400/mo) this would more than pay even if I had to borrow the money. $6k for 3 yrs at 10% interest is under $200/mo,, so boondocking 6 months out of the year would pay for itself – and the equipment should last far longer than 3 years, letting one save some money for a sweet bank of lithium batteries without dipping into the budget. Plus how can you put a price on living in style and air conditioned comfort, in relative solitude, in some of the most beautiful, remote wilderness places in America?
Chip
Chris Dunphy says
The key is thinking it through, and having realistic expectations. You are absolutely on the right track, and it sounds like you have worked out an awesome plan. Great work!
beagle123 says
Hi Chip. One thing that most people don’t consider is that lithium batteries last much much longer than lead. That lowers the cost per charge very significantly. Also, I’ve heard that draining lead batteries to their limit damages their lifespan which makes them more expensive. I heard the recommendation that you only drain lead batteries half way to preserve them, so essentially you then could be purchasing about half as many lithium batteries for the same capacity.
The real cost of batteries is the real capacity multiplied by the number of cycles of use:
Lead = 500ah X 50% X 300 cycles = 75000ah
Lithium = 300ah X 80% X 1000cycles = 240000ah
Something like that. So you might get triple the capacity from the smaller lithium battery so it might justify spending more money.
Chris Dunphy says
Indeed – we’ve written a lot about the potential for the lifetime cost of an LFP bank proving to be a lot cheaper in the long run than lead. Our lithium series of posts has our initial cost analysis.
But it is still a theoretical advantage though. As we’ve written about recently, our LFP batteries have aged faster than they should have.
– Chris
George Zeiler says
Thank you so much for writing this post, what a wealth of information! I like the idea of the mini split a/c, although, like you say, we would have to get creative with finding the right location for both pieces.
Eric Udell says
Great article, Chris. I’ve done the ( very ) short form of this explanation a few times in different forums to help others understand the basics of the challenge of solar A/C. Now, all I need to do is post a link to your explanation.
Keep up the good work.
Chris Dunphy says
I think we’ve all probably had some form of that conversation at various times – so the goal with this post was to just write it all down in once place.
I hope this becomes a linked-to FAQ for everyone interested in keeping cool in an RV off of solar power.
Al Christensen says
I know a guy who got around the problem of solar panels vs. rooftop clutter. He had a rack built over all that stuff. His panels are always in the clear.
Jfet says
We built our own RV from scratch and have a entirely flat roof capable of holding 2000+ watts of panels. Right now we have 1080 watts for starters. We have a small through wall window unit with custom ducting so it is mounted flush with the outside and extra insulation. It draws 4.8amps at 115VAC and is rated at 6000 BTU. We used 2+ inches of polyiso insulation throughout the RV. The living space is small, so the 6000 BTU cools it nicely. I like the more efficient mini split but our through wall unit was $100. We use a Magnum hybrid 4kw inverter running on a 24V battery system.
I don’t think we can go 100% solar A/C with our current level of solar and battery bank but it would not be hard to upgrade to that point when Lithium gets more mainstream.
Chris Dunphy says
Sounds like a great system – nice to see yet another example of making it work, and just how much is involved to do it.
Thanks for sharing!
John says
I’ve been following your blog for a while now. As a EE I really enjoy your posts related to technology. I’ve been modifying my 2007 Georgetown 350DS for about 8 years now. One of the most exciting projects I have taken on is solar powered AC. I completed my design and installed it 3 years ago. The results are quite amazing. I would agree this type of project is not for your average RVer. But any technical person with the right motivation can succeed. I could spend hours discussing my system setup. But to keep this comment concise I’ll simply list the components that make up the system and a few of the tasks involved.
-remove both front and back stock AC units. RV manufacturers aren’t required to use high SEER rated AC units like you would find in a house. My stocks units pulled 2000 watts on high. Removed, sold for $250 each.
-removed the 6500 watt Generac gasoline generator. I’m trying to reduce gasoline usage since I do a lot of boondocking. Sold to a guy who installed it in his high mountain cabin for $950.
-Tinted the all the house (back) windows with limo black tint. Tinted to driver and passenger windows with 35% tint. This was a low cost but big payoff step. Heat soak inside was reduced dramatically.
-Installed 8 230 watt Sharp solar panels at a cost of $0.75 a watt off ebay. With the AC units installed you gain a lot of roof space. 85-90% of the roof is covered with a few open areas where the roof vents and shower bubble protrude. I mounted them flat with a ~1 inch air gap for cooling. I really don’t like the idea of tilting panels on the roof. Mechanical failure of mounts and climbing to the roof each stop is not appealing. Beside 1800 watts panels is sufficient. With the flat mounting I see about 1500 watts at high noon in the summer.
-Installed (6) 12 VDC 120 Ah 29DC lead acid batteries in a welded tray I placed where the old generator was. I’ve though of going with Lithium but the price is too high. I can get the lead acid batteries for $85 at Walmart. (One of my next tasks is to create my own NiFE battery bank. NiFe batteries are very very rugged. The extra weight is not a factor in such a large RV.)
-Installed a mini split AC unit. I bought the 9000 BTU unit from highseer.com. It uses only 750 – 800 watts on high and only requires 110 VAC. Many of the larger units require 220 VAC. It’s very very quiet. I hung the compressor on the supplied mounts off the back of the RV. I removed the front TV located above the cockpit and mounted the evaporator. We rarely used the TV and the location was perfect for inside unit. Running the compressor lines 40 feet to the front was a challenge. I followed the chassis frame rail and wrapped both pipes in insulating foam protective tape.
-Installed a 3500 watt continuous / 7000 watt peak DC to AC inverter. It’s not pure sine wave. This AC unit runs fine on modified sine wave. I save some cost by not having a pure sine wave unit.
I could go into more details, but you get the picture.
Chris Dunphy says
Thanks for sharing John – you’ve clearly done a great job! And you certainly demonstrate just how much work is involved in this sort of undertaking too!
Do you have just one cooling zone setup? Any issues with the single 9000 BTU AC doing the job formerly handled by two 13,000+ BTU roof units?
Thanks for sharing your setup,
– Chris
John says
I’ve got just the one zone. The bedroom can get a little warm, especially before I added the tint. I solve this with a small circulating fan on the floor. Longer term I am installing 2 low profile ceiling fans in the recess where the old AC units were.
You raise an interesting point. As I’ve gone though the systems in the motorhome, I’ve found that RV manuafacturers are not interested in efficiency or ingenuity. Their solution to cooling RVs down is throwing more watts at problem. I don’t see any system in my RV that isn’t an exact copy of what was used 10 years ago or today. They reuse the same equipment over and over in each new model year.
And another interesting trend I’ve seen lately…motorhomes with dark painted exteriors. I bet it gets really hot in there. I supposed they solved this problem with a 3rd AC unit.
Anyway, I find tinkering on the RV fun. It’s a great hobby for me. Did I also mention I’ve piggy backed a CNG fuel system on the gas engine? That was a lot of fun.
Ben P says
Can anyone confirm my AC unit math? BTUs / SEER rating = electric Watts right?
So a dual zone 12k BTU Thermocore Systems unit ( http://www.amazon.com/dp/B00TYARIUC/ref=twister_B00Q2J1TLM?_encoding=UTF8&psc=1) with a 21 SEER rating and 24k total BTUs would only consume 1143W at max? I do assume we’re talking max average and not peak (start up)…
24,000 BTU / 21 SEER = ~1143W
1143W x 24hrs = ~27.4kWh
So it would consume about 27.4kWh in 24hrs with a 100% Cooling Cycle? That seems pretty ridiculous considering Chris’s rear AC consumes 42kWh…
Chris Dunphy says
You’ve almost got it: BTU / EER = watts.
SEER (seasonal energy efficiency ratio) is slightly different than EER (energy efficiency ratio) because it takes into account the performance over the course of an entire year, as opposed to just a particular set test condition.
According to the Wikipedia article on SEER: “A SEER of 13 is approximately equivalent to an EER of 11”.
It is no surprise though that a mini-split with a 21 SEER rating can blow our RV AC’s out of the the water when it comes to efficiency. When I was playing with numbers, I calculated various RV roof airs having EER ratings between 5.67 (Atwood AirCommand) and 11.34 (Coleman Mach 3 PS) based upon their published specs.
The 15,000 BTU Mach 8 I calculated to have an EER of 10.20. Our Dometic Penguin I calculated to have an EER or 7.94.
There is clearly a LOT of room for improvement. I’d love to see an RV AC with a SEER over 20. Maybe someday!
– Chris
Ben P says
Thanks Chris!
The EER for that unit is listed at 11.5 ( http://www.thermospace.com/ductless_split/thermocore-t121d-h218-12+12.php ). That makes a lot more sense. Power draw a little over 2000W and a 24hr 100% Cooling Cycle at a smidge over 50kWh.
Ben P says
Thanks. Given me some more things to think about…
I keep wondering about a huge lithium battery bank. A 50kWh pack would give you about 24hrs of use with a 2 unit AC rig with a 50% usage cycle without plugging in, running a generator, or using solar. If my maths are right, a 45 cell 400Ah CALB lithium pack would give you 57kWh. The cells would cost about $24k from a US electric car conversion parts supplier, and weight about 1400 lbs. Nominal 144V if wired in series, pretty perfect for a 48V system. I’m half expecting such a pack to get down around $12k in 5 years time too.
Random thoughts: A pack that size in a 3×15 cell arrangement would be 51.1″L x 42″W x 11.1″H. Insulating the pack with some 2″ rigid foam insulation and leaving some wiggle room for cables on top gets you somewhere in the range of 56″L x 48″W x 18″H. /me wonders if that would fit in a single Class A bay… A little too big I suppose.
Chris Dunphy says
That would be an amazing amount of power to cart around. There are electric bus designs that are just coming to market that I believe have battery banks that large, but it will take a while for the costs to come down.
One challenge will be charging a battery that large after you’ve drained it.
A lot of fun engineering problems to solve… *grin*
– Chris
Ben P says
Electric buses or all electric coaches? The BYD electric bus is about 300kWh: http://www.byd.com/na/auto/ElectricBus.html The Motive E-450 conversion buses can be ordered with 80/100/120kWh: http://motivps.com/portfolio/the-all-electric-e450/ The BYD seems to have some customers. No idea how real of a product the Motiv is.
Yeah, charging is an issue.
Chris, have you ran across Tony Seba yet? Just wondering if you had and what you thought about him and his predictions: https://www.youtube.com/watch?v=RBkND76J91k He makes some pretty wild predictions that would have a pretty serious effect on coach batteries in the next 5-10 years, with the real possibility of “affordable” < $250,000 all electric Class As (think Tesla, not Etrek) in 10-20 years.
Romana Starfield says
I have a small bus which has a purpose built 240 volt (I’m in Australia) campervan airconditioner. I have 700 watts of solar panels and 390 AH of batteries. I have no problem running that air conditioner off of that system with no voltage drop on sunny days intil the evening. http://www.carliving.info/blogwp/?p=815
Chris Dunphy says
Looks like you’ve but together a nice setup. And indeed, it can be done with the right gear and careful optimization. Thanks for sharing!
Kathryn Johnson says
Ummmm, the above comment was for richard bateman, it said it was pisting to richard so not sure why it posted here, but tgat means i read your question and so will comment (lol)
My post to you is…
Australia uses 240 Volt systems. At 240V less current is required. W = Volts x Amps. The amount of power required to run your equipment, is half that of 120V systems, which is what USA uses, so it can’t be compared to USA.
Watts = the total power potential of the system.
Amps = the actual electrical current
Volts = the force that drives the the current through a conductive medium such as metal wiring, etc
Anytime you increase the voltage to a system, the current required to give the same amount if power is reduced proportionally. For instance, a 1200W microwave in the USA uses 10amps of current, whereas that same microwave in Australia uses only 5amps. Therefore, your batteries will last twice as long as those in the USA running the same equipment.
Nikki says
Oh man, I am glad you wrote this post so I don’t have too! And I couldn’t have said it any better! Great info about an often asked question.
dwmac71 says
Some years back I saw a 12vdc roof top a/c unit made for semi trucks that ran off an extra bank of batteries. But trucks have very little to no insulation so the batteries would drain before the 10 rest break was up. I think the company was called dc airco from Europe.
They seem to work fine in the European truck which have a much smaller sleeper compartment and a 24 vdc power system.
Looking forward to your next post
jackdanmayer says
Great synopsis of the current state of things. While it IS possible to cool with battery/solar – I’ve doe a few installations – it has all the limitations you discuss. Excellent.
Michael Miller says
Very well done article. You identified the complexity of alternative energy solutions. No one source will be enough to replace the grid.
Next up, a wind turbine at the top of your flagpole?
Chris Dunphy says
We know a few RVers who have used wind turbines, but they require significant setup and takedown efforts, are noisy, and of course you need sustained wind.
In much of the places RVers like to go, gentle breezes are more typical than strong sustained winds – making wind power gear just a lot of ballast to carry around. But for the places it makes sense, you can get a decent amount of power – potentially day AND night.
– Chris
Wade Bowie says
Great article guys! I really enjoyed it. Thanks. I guess it’s time to put that two foot thick cob coating on the outside of our new bounder to increase its R-value. I’ve always wanted to try it but so far I haven’t figured out how to do the slides. 😉
Chris Dunphy says
A cob encrusted Bounder sure would be a sight! *laugh*
Jodee Gravel says
Some day……..but until then we’ll just aim for the cooler temps as much as possible and save the solar for everything else 🙂
Jill Sessa says
Love your geeky-side exploring this and truly showing what it takes. Me? I’m much like you in that I’d rather move my home to match my favorite temps than battle the elements to “sit in a cooled off tube”.
I get surprisingly plenty of cool out of these tiny 12V fans they sell at West Marine. Cageless (just two blades) and two settings. They seem to sip energy rather than gulp and I can point them right to where we need the air circulating.
And huh, the irony that a swamp cooler wouldn’t actually work in a swamp environment is just another example of the oddities of the American English language 🙂
Thanks, Chris!
Scot Mealy says
Thanks for this! I was curious and this was very well thought out and presented clearly.