We’re currently driveway surfing with friends in coastal Georgia, where it’s pretty darn hot (and crazy humid!) as the summer fast approaches.
They only have a 15A power outlet on a front porch available for us to plug a long extension cord into, which for many RVs would mean blowing breakers or limping along without being able to run heavy loads like a microwave or an air conditioner.
But making a hot lunch while staying cool is no problem at all for us thanks to the way we have our electrical system setup.
We’ve written about our system before, but as we were watching readings on our Victron CCGX Control Panel showing power combining from the shore, the sun, and our batteries to keep our roof air conditioner cranking along, I told Chris:
We should totally video this!
So we did – and created this little video that shows how all three power sources come together to give us such an incredible amount of flexibility:
Here are some past posts where we’ve talked before about the individual components of our electrical setup:
- Lithium Batteries (500AH at 12v)
- Boosting Hybrid Inverter (Victron MultiPlus 12/3000VA)
- Solar Setup (800W on the roof, 600W ground deploy)
We’ve been using this setup for nearly 5 years now (the battery & inverter since 2011, the solar added in 2014)… and we have had so many occasions where the increased flexibility has really paid off for us.
A few examples:
- When we endured our 7 week engine rebuild, it enabled us to live onsite in the bus, apprentice during the project, and not melt in the parking lot despite just having a 15A extension cord for power.
- We’ve been able to frequently optimize our view by pulling straight in and using a long extension cord instead of our thick short 50A shore power cord, and even still we can use both ACs during the heat of the day.
- And of course, when it’s not ridiculously hot out, we enjoy a great deal of off-grid camping while being abundantly self contained with our huge tanks and ample solar setup.
Why Not Solar AC?!?
We do get asked all the time about going all-in to run our air conditioners entirely off of solar.
And, well, it is possible.
But it requires a LOT more solar than most people realize, and it is not at all easy to fit that much solar onto an RV roof.
In our case, it would actually be impossible to fit anywhere close to enough solar on the roof without removing (or building over) the roof air conditioners entirely, which kind of defeats the point.
Instead – we consciously decided to optimize our setup for running our air conditioning entirely off battery power, with solar as a supplement.
We can run our AC full blast for 2-2.5 hours, powered only by our 500AH LFP batteries. Whatever sun power we do collect of course extends that run time out significantly.
But if the heat is too extreme to need the AC for more than an hour or two a day – it’s time to retreat to electrical hook-ups, or resort to our 2500w propane-powered generator to supplement the peak demand.
Running an AC this way depletes the batteries, power we also need to run our 12v powered Vitrifrigo marine fridge, computers, lights and cooking (our primary cooking devices are all electric: a single induction stovetop, InstaPot pressure cooker, microwave/convection oven and rice cooker).
Power that has to be restored from somewhere, and at the end of sunny hot day when we might be able to turn off the AC – there’s not much sun left to top up the batteries.
Flexibility Is Key
Our setup has always been about optimizing flexibility. We enjoy stays in public parks, boondocking in the wilds, on friend’s land, and even the occasional full hook-up parks.
The ability to run our AC off batteries was initially designed so we could make stops on driving days and keep the RV cool for Kiki while we attended to errands or touristy things.
Our general rule of thumb – if it’s hot enough for regular AC, it’s really time to be seeking cooler temperatures.
After all, that’s why our house has wheels.
If it’s hot enough to need regular air conditioning, then our quality of life is diminishing all around. We’re spending too much time indoors trying to keep cool, and not enough time outdoors doing the stuff we love.
And honestly, we just can’t imagine too many scenarios where we would HAVE to endure extended warm temperatures and not have access to at least enough shore power to supplement the solar.
Maybe one day solar panels will be more efficient, or we’ll increase our battery bank size. That would give us even more capability and flexibility.
But until then, we’ve been extremely happy with our setup.
Before You Ask…
We’ve already had some questions asked over and over in response to this YouTube video, and it has only been up for a few hours. So before you ask…
- Why don’t you use more powerful solar panels? – There are more powerful solar panels to be had, but they are proportionally physically larger. With our curved roof layout, larger panels would not have worked.Our GS-100 panels are small (about 40″ x 20″ each), but they are actually some of the most efficient panels produced. Our panels use Sunpower cells and have an overall module efficiency of 18.3%. That is just about the best you can get from mass produced panels, though Sunpower was able to bring a 20% and 21% version to market in a large form factor for buildings.The world record module efficiency in a lab was recently pushed to 22.8% and then just this March to 23.8%. But those modules are still far from being commercially available.
So… No – there is nothing even in a lab right now that would significantly increase our power production in the same space. If it existed, we’d be all over buying it.
Why don’t you tilt for more power? – Indeed, we could get 20% – 30% more power in the winter by tilting our panels, and when we are stopped for a long time we do have the hardware installed to do it (and have). But tilting does not make nearly as much difference in the summer (when AC is needed) when the sun isn’t at such an extreme angle.With our curved roof it is often way more trouble (and risk) than it is worth. We’d love to have some sort of magical tilting system that could be deployed from the ground (if there happens to be any enterprising engineers out there wanting to bring such a product to market – do be in touch.) So when we are stopped for a while and want extra power, we have 600w of flexible solar panels we set out on the ground.
But even with tilting and our extra panels, it would still take way more panels to go 100% solar while running an AC.
Our friends The RV Geeks just put out an awesome video & article explaining the benefits of tilting solar panels if you’d like more information.
- Do you have / need a soft start? – When our friends The Wynn’s published their video & article on running air conditioning for a bit off their solar (which they, like us, are actually running off batteries and supplementing with solar) they talked about a soft start for their AC.When an air conditioning compressor kicks on, there is a huge momentary surge current that can overload many inverters. Our Victron MultiPlus has enough momentary surge capacity that it has never had a problem with our air conditioners cycling, but at some point we may still add a soft-start kit to our roof ACs to vastly decrease the surge.
- You don’t actually need lithium batteries to do this, do you? – No, of course not. If you design a large enough lead battery system to spread the current across enough parallel batteries you can reduce the impact of pulling high-currents. But you can only do so much to get around Peukert’s Law and your lead batteries draining extra quickly when under such a heavy load.And that just means you’ll need more solar and/or generator time later to make that power loss back up.It can be done – but it has disadvantages compared to lithium.
- Seriously – running a roof AC off solar is no big deal… – Indeed, we’ve said over and over and over that it CAN be done, especially if you make doing so a primary design goal building or refurbishing a rig from scratch. That is why our featured post on the topic is The (Almost) Fantasy of Solar-Powered RV Air Conditioning.If you are willing to make the tradeoffs, go for it! We personally prefer to head for cooler temps, so we can have a better quality of life all around by keeping windows open and being comfortably outdoors exploring.
- How are your lithium batteries working out? – August will mark our five year anniversary living with our lithium batteries, and we’ve logged more time with this sort of setup than just about anyone. We’re planning to do some stress tests on our batteries once they reach five years old to see how they’ve aged, and will issue another update on our batteries and power system then.
Until then… keep cool and carry on! We’re making our way north to cooler temps to escape the drone of our ACs.