“Hey Andy, can I run my RV air conditioner on batteries alone? 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 pops up so much.
Every RVer who has ever spent an evening on a beach, BLM dispersed campground, or a Cracker Barrel parking lot has wondered, “What do I need to run my RV air conditioner off battery power?”
I hope you’re sitting down, because some of you will have to choose between your child’s college fund and your dry camping comfort.
So what’s the answer?
Eh … no – not unless you want to invest many thousands of dollars in upgraded batteries and a whole-house inverter system. Unless you’re a die-hard boondocker with cash to burn, you’ll have to operate your air conditioner off generator power.
If you’re still interested, then fair warning: This is a deep rabbit hole. New batteries are just the tip of the iceberg. You’ll probably wind up paying for a new power system. Let’s dig in.
Running Your RV Air Conditioner on Batteries
There’s a lot of hogwash out there about what it actually takes to power your air conditioners when using nothing but battery power. One popular article states, “It is possible to run your RV air conditioner off a battery but it may take two to get the power and longevity you need to cool your RV down.”
Two batteries, you say? Bologna! Try at least 4-6 batteries, preferably lithium batteries. With 2-3 batteries, you won’t have more than 1-2 hours of run-time, which just isn’t enough for a weekend camping trip – or even an overnight stay at a Cracker Barrel.
But like I said, this is a deep rabbit hole. The big challenge (besides energy storage) is that, as I’ve written about, typical RV air conditioners aren’t very efficient. If you want maximum cooling and performance, you need to replace your stock air conditioners with high-efficiency models, 12V truck air conditioners, or even swap them out for residential mini-split units. If that sounds like a lot of work – it absolutely is, and it’s way beyond DIY for most people.
>>> Read More: 4 Best High-Efficiency RV Air Conditioners for Boondocking
I also must warn you that upgrading your power system to run air conditioners off battery power usually involves large (100+ amp) electrical currents and big, thiccc wire – we’re talking up to 2/0 AWG cable, which is almost as big as my pinky! Working with large wire requires special tools and safety precautions; a loose connection can easily generate enough heat to start an RV fire!
I’ll get off my soapbox, but I just want to be honest about the scope of this upgrade. It’s B.I.G. This article only scratches the surface.
What Type of Electricity Is Required by an RV Rooftop Air Conditioner?
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.
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 of the abbreviation. AC is Alternating Current; DC is Direct Current. AC electricity comes from your generator, inverter (if equipped) and shore power cord; DC electricity comes from your batteries and converter.
(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).
>>> READ MORE: If you’re not sure what some of these terms mean, check out my RV glossary.
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. You need a man in the middle: an inverter, to feed it the correct kind of electricity. More on that later.
How Many Watts Does It Take to Run an RV Air Conditioner?
Air conditioners are thirsty, thirsty devices. They “drink” a LOT of power! And a battery can only store so much juice. That’s the first challenge: Where do you store all this power?
Now, 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 100 amp-hours (Ah)? You can use up to 50Ah. Any more than that, and you’ll drastically shorten the battery lifespan.
>>> Read More: The Geek’s Guide How to Murder Your RV Battery
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 right now. 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 11-13 AC amps while in continuous cooling mode on a hot summer’s day. A 15k BTU air conditioner draws 14-18 amps for the same.
With a little number crunching, we also find out the average 13.5k BTU RV air conditioner draws 1,100 to 1,400 watts, and the average 15k BTU RV air conditioner draws 1,350 to 1,800 watts. The faster the fan speed and the higher the outdoor temperature, the more power the unit will draw.
How Many Batteries Does an RV Air Conditioner Use?
Let’s begin by asking a hypothetical question:
- Q: How long could you run a stock RV air conditioner off your standard 100Ah lead-acid house battery (if you had an inverter that could handle the draw)?
- A: About 20 minutes. Which would almost certainly and irreversibly damage your battery.
That’s our benchmark, people. Enough time to steep a cup of tea.
I’m going to spare you the nitty-gritty math. (If you want to do it yourself, then convert everything into watts so you can correctly compare battery watt-hours to air conditioner wattage requirements. Don’t forget to account for peak cooling requirements, duty cycle, inverter losses, discharge rates, and other loss factors.)
Here’s the short answer: You need a minimum of 600 useable amp-hours at 12 volts to run ONE (1) RV air conditioner off battery power.
Emphasis on the term “useable.” If you’re using lithium batteries, you’ll need about 20% more than the nominal, so around 700 amp-hours of 12-volt batteries. If you’re using lead-acid deep-cycle batteries, you need twice as many: figure 1,200 amp-hours of 12-volt batteries. It also helps if you have a solar panel array to replenish some of the lost juice.
For reference, the typical RV house battery is a paltry 100 amp-hours. So you’re talking at least half a dozen batteries (that’s around 250-500 lbs. of batteries, mind you) plus a 2,000-watt inverter (or larger) to run your RV air conditioner for … wait for it … drum roll …
About four continuous hours of cooling.
Yup, all that work, all that money, all that work, and you might be able to enjoy a 1-day camping trip. And remember – this is for a single air conditioner. If you have multiple air conditioners, you’ll need to multiply these estimates.
What Parts Do I Need to Run My Air Conditioner Off-Grid?
If you’re a glutton for punishment and you’re still holding out hope, then here’s the last big piece of the puzzle.
Like we talked about, RV air conditioners run on 120-volt AC electricity, not DC. But your batteries only produce DC electricity. Thankfully, there’s a nifty device called an “inverter” that magically transforms 12VDC to 120VAC power.
>>> READ MORE: Check out my deep dive on RV inverters!
RV inverters come in many flavors. The typical RV inverter is a 2,000-watt pass-through inverter that is only capable of powering a handful of low-power circuits. They typically can’t handle the continuous power draw of an air conditioner.
If you want to run your 13k+ BTU RV air conditioner through an inverter, you’ll need a heavy-duty whole-house inverter like the Xantrex FREEDOM XC PRO 3000, Victron Multiplus 3kVA, etc. – plus about a dozen accessory and complementary parts I haven’t mentioned.
How Expensive Is It to Run My RV Air Conditioners Off Battery Power?
When you start talking about running your RV air conditioner off batteries alone, you’re just tipping over the first domino. Soon you start talking about solar panels to replenish all those batteries, auto-switching uninterruptible power supplies, load management systems …
It can easily cost $10,000+ to retrofit your RV this way. If you’re wanting to run 2-3 air conditioners off-grid, it can easily cost $20,000 just in parts. Even the simplest retrofits will cost at least $3,000+.
>>> READ MORE: For a more in-depth look at how long you can run other RV appliances off your battery, check out my RV Battery Life article series.
So what’s the verdict? Can you run my RV AC off the battery? Ehh … if you’re rich, sure! For the rest of us, tote along a generator, buy a Zero Breeze portable air conditioner, or pay for a night at the local KOA.
The Solution: Run a Generator!
The truth is, most RVs don’t even have the cargo capacity to handle all those batteries … And you’d have to become a veritable expert in RV electricity to rewire your power system. 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 the battery? – Use a generator!
>>> READ MORE: 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.