“Hey, Ross, can I run my RV AC on battery? I want to go boondocking for the weekend and I don’t have a generator.”
If I had a dollar every time I’ve been asked this question, I could (maybe) afford one payment on the new iPhone.
I’ve even helped warranty service and customer techs draft template responses to this question because it comes up so much.
TL;DR: You could, but you really don’t want to.
Electricity Required for an RV Rooftop AC
Let’s imagine your RV air conditioner is a calf, alright?
(It’s a weird analogy, but hey, work with me.)
A calf can only live on milk, not Kool-Aid. In the same way, an RV rooftop air conditioner can only run on a certain “type” of electricity.
FYI: If you’re not sure what some of these terms mean, check out my RV glossary.
There are two types of electric power in a typical RV. Their shorthand names are 120VAC and 12VDC, or sometimes just “AC” and “DC.” Everyone expects you to know the rest, like you’re in some sort of club.
(By the way, you might see numbers calling out 110, 115, 120, or even 125 volts. For our purposes, these all mean the same thing).
When you plug into shore power at a campground, the campground feeds your system with 120VAC power and wallah! – your AC works! You stop sweating! You can actually breathe! Hurray!
A battery simply can’t produce that kind of power. It can only produce 12VDC electricity. You just can’t get milk out of a Kool-Aid tree, no matter how hard you squeeze.
You cannot directly run your RV AC off the battery.
Can I Invert DC Power to Run My RV AC?
Now, there’s a nifty device called an “inverter” that magically transforms 12VDC to 120VAC power.
Unfortunately, there’s another problem: Power requirements.
Goats make milk. But you can’t raise a calf into a big, strong bull off a goat. Goats don’t make enough milk!
Air conditioners are thirsty, thirsty devices. They “drink” a LOT of power! And a battery can only store so much juice.
RV house batteries are rated in amp-hours (Ah). A common size is 100-Ah.*
*I promised myself I wouldn’t dive into battery science, which is a whole other topic, but YOU SHOULD KNOW that – unless your battery is a lithium battery, like BattleBorn – you can only use about HALF the stated capacity of a standard lead-acid deep-cycle battery. Battery rated for 100Ah? You can use up to 50Ah. Any more than that, and you’ll drastically shorten its lifespan.
RV air conditioners are usually rated in an archaic unit called BTUs, commonly ranging from 8,000 to 18,000, with 13,500 (13.5k) and 15,000 (15k) being the most popular sizes.
How BTUs are calculated isn’t important. The bigger the RV, the bigger the AC should be. Some RVs have two or even three air conditioners! The rule of thumb is 1,000 BTUs per ft of RV body length.
Once you move around a bunch of numbers, you find that a typical 13.5K BTU air conditioner draws, say, about 12-13 AC amps while in continuous cooling mode on a hot summer’s day.
When converted to DC amps, that’s about 120-130 DC amps. Yikes!
Based on these numbers, if you invert power from a normal 100-AH battery to 120VAC power, a 13.5K BTU RV rooftop air conditioner, running continuously, will deplete the usable capacity of the battery in about 20-25 minutes. (And for various scientific reasons, it’ll actually be quite a bit less).
In the same way you shouldn’t ask a cow to produce 10 gallons of milk an hour, so you shouldn’t expect a battery to give away all its juice so quickly. That will quickly damage or even ruin your battery.
So what’s the verdict?
“Can I run my RV AC off battery?” – Ehh … no.
For a more in-depth look at how long you can run your RV off your battery, check out my RV Battery Life article series.
The Solution: Run a Generator
Theoretically, you could buy a horde of true deep-cycle batteries, wire them in parallel, purchase a $3,000 inverter, and run your AC for a weekend just fine.
‘Course, that would cost about $6,000+ in parts and weigh several hundred pounds . . .
And you’d have to become a veritable expert in RV electricity to rewire your converter. And you’d need a much larger solar panel system to charge all those batteries, upgraded multi-stage charter, additional surge protection …
You get the picture.
You want to feed a calf? Find a cow.
You want to run your air conditioner off-grid? Run my RV AC off battery? – Use a generator!*
*See this article for an in-depth look at generators and solar power comparisons!
A Quick RV Air Conditioner Bonus Tip
Oh, and one more thing, readers:
All those cheap “portable” air conditioners you find online?
Please, for the sake of all Petes, ignore them.
They aren’t “real” air conditioners. Real compressor air conditioners actually make more heat than cold, which is why they must be vented to the outdoors.
If someone’s selling a “portable indoor air conditioner,” it’s almost certainly just some version of a fan blowing over cold water.
Unless you live in an arid climate, they will do absolutely no good, and will probably just turn your RV interior into a humid, muggy swamp.