Solar + Battery Powered RV Air Conditioning: Off Grid AC?!

Can you run an RV air conditioner with solar power, using 12 volt RV batteries? That’s the question every boondocker wants to know when the summer heat comes around, and air conditioning is a luxury.

The answer is technically yes – if you have enough high quality, lithium batteries, and a big enough solar array to keep them charged.

But whether it’s cost effective is a different story. For the number of 12 volt batteries you’d need to run an RV air conditioner off grid, it’s probably more cost-effective to simply buy a generator to run your RV AC.

Air conditioner compressors and fans are very energy-intensive on start, and to keep running and actually cool your camper. Based on the average rooftop RV air conditioner which is 15,000 BTUs, you’d be using 3,500 watts to start up and 1,500 sustained watts to keep running.

How Many 12V Batteries Will Run an RV AC

If the average 15000 BTU air conditioner runs at 1,500 watts, we will convert this into amp hours. At one hour of use, 1500 watts divided by 120 volts is 12.5 AC amp hours. To convert this to DC amp hours, you multiply by 10, so 125 amp hours. So with 3 12 volt batteries at 100AH each, making 300 amp hours total, you can run your air conditioner for about 2.4 hours – almost 2 and a half hours.

BUT that also means that you’re using 100% of your amp hour capacity, so you have no power left for overnight or other electrical items you may want to run. AND that also assumes that your batteries are lithium ion, which you can run down 100%. If your batteries are lead acid or AGM, you can only use 50% of their amp hour capacity without ruining the battery – so you would need a 600 AH battery bank, or about 6 12 volt batteries, just to run your RV air conditioner for 2 and a half hours, without running anything else.

Cost to Run Typical RV AC on Lithium Ion Batteries

So as you can see, if you’re trying to run your air conditioner off grid, you’re going to need a lot of batteries. What’s the cost of all of this?

The typical 12 volt 100AH lithium ion battery runs about $500-900. So just for 300AH of capacity, you’ll be spending $1500-3000 up front, and will still only get a few hours of run-time.

Most people who actually run their RV air conditioner off of batteries have between 400-800AH of usable power in their off-grid battery banks. So a good rule of thumb if you’re determined to have off-grid solar power is to plan for having 4 to 8 12 volt batteries.

You’ll also need enough solar to keep those batteries charged. A general rule of thumb is that you should have twice the wattage of your amp hour needs. So if you have 400AH of usable battery power, you should have a minimum of 800 watts of solar. Likewise if you have 800AH of battery capacity, it’s a good idea to have 1600 watts of solar.

As you can see, the costs really add up! 400-800 AH of lithium ion batteries plus 800-1600 watts of solar is pretty expensive, even when installing your solar system yourself.

More Efficient Off Grid Solar RV Air Conditioners

What if you use a different air conditioner? That’s a possibility! Many off-grid RVers will use an efficient mini-split air conditioner, which takes a tiny fraction of the amount of power required to run a regular RV air conditioner.

If you choose a more efficient AC, you can run it for a lot longer and less power. However, keep in mind that mini-split systems can be quite costly and require a bit of advanced installation. If this is something you’re interested in, you will probably already know which mini-split systems will work in your RV and are just looking for amp hour capacity! In that case, you should use the formula above with your air conditioner’s power specs to figure out the AH usage based on the number of hours you’d like to use it for each day.

What are your thoughts? Will you build an off-grid system that can power your RV air conditioner to keep you cool when boondocking? Sound off in the comments!

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