You will need at least 1,800 watts of solar panels to run your RV air conditioner for 8 hours each day. This is assuming you are using 12 volt RV grade panels. This is also assuming, of course, you have a lot of battery power too.
How Many Solar Panels Do I Need to Run My RV AC?
It all depends on how many hours you want to run your AC unit, and how AC units you have…
- If you want to run a single AC unit for about 8 hours each day, using batteries and solar, we suggest about 1,800 watts of solar (both mounted on the roof and on the ground), along with a battery bank of 800 amp hours (AH). This is a very large configuration which very few boondockers have, and it’s mostly because it’s very expensive, and very heavy in weight.
Most boondockers have between 400 to 800 watts of solar, and between 200 to 400 amp hour battery banks. Suffice it to say, most boondockers don’t run their AC unit from solar and battery. They rely on generator for that.
If you still want to run your AC unit from solar and battery, keep in mind that you will also want to run other appliances and components as well. On top of that, you have to make sure your batteries still have a full charge after the sun goes down.
How Much Power Does it Take to Run an AC Unit?
If you want to run your RV air conditioner on solar and battery, remember that a typical RV air conditioning unit outputs 15,000 BTUs of cooling power. These AC units generally require about 3,500 watts of power just to start up, and then about 1,500 watts just to keep running. AC units demand so much electricity, that nearly all RVs are incapable of running them off of their factory battery & solar configurations.
You can also install a “soft start” component (see it on Amazon) to an RV AC unit. This will force the AC unit to start up slowly, thereby requiring less start up power. Thus, an AC unit normally needing 3,500 watts to start up, can now start up with 1,500 to 2,000 watts.
24 Volt Solar Panels vs. 12 Volt Panels
Most solar panels sold for RV use run on 12 volts. These are the more narrow, rectangular panels (like that depicted on the photo above). Most 12 volt panels produce a maximum of 150 to 200 watts.
But many boondockers are opting for residential-grade solar panels which run on 24 volts. These are physically larger in shape, basically like two 12 volt panels creating a square-shaped configuration. Because they are physically larger in area, they produce more wattage, usually 350-400 watts.
The reason why many boondockers are switching to 24 volt panels…
- Their physical shape and dimensions may fit better on an RV roof depending on what available real estate is up there.
- Because they produce double the wattage of 12 volt panels, they require fewer panels, translating to fewer cables and connectors.
- 24 volt panels are compatible with a wider range of batteries and solar charge controllers, offering more choices for boondockers.
Tesla Car Batteries Are Becoming Popular with RVers
The BoonDoctor, a mobile RV technician, installs Tesla Model S car batteries into RVs, usually a set of two or three, specifically for the purpose of running air conditioning units off of solar & battery.
Each Tesla module produces about 200 to 220 amp hours of power, but at 24 volts. This is equivalent to four 12 volt, 100 amp hour lithium batteries (think Battleborn, Relion, et al). So, two Tesla Model S batteries, is equivalent to about eight or nine 12 volt lithium batteries.
BoonDoctor will mount 800 to 1,000 watts of 24 volt panels.
So, given the higher output of Tesla Model S car batteries, and the higher efficiency of 24 volt panels, it still requires a minimum of 1,000 watts of these panels, with about 400 to 440 amp hours of the 24 volt, higher efficiency batteries.
The Cost of Solar Panels
There is a general rule of thumb when it comes to the cost of solar panels… The cost is $1.00 per watt. Thus, a 200 watt panel is generally going to cost $200.00. This figure is for the price of a single panel by a consumer through a retail channel like Amazon or Camping World.
If you hire an RV shop or mobile technician, your cost will be at least double that, about $2.00 per watt, because of the cost of wiring, mounting hardware, and labor.
Monocrystalline vs. Polycrystalline Panels
If you want higher efficiency panels, go with monocrystalline. These panels have a black color appearance. They are more expensive to produce, and are thus more expensive to buy.
Polycrystalline panels are the cheaper option. These panels have a blue color appearance. They are faster and easier to produce, thus cost less to buy, but are less efficient at converting solar into electricity.
Almost all boondockers go with monocrystalline panels because the roof of an RV is very limited in space. Polycrystalline panels make more sense for small applications like powering home security lighting, or in cases where you have lots of roof real estate.
Roof Mounted Panels vs. Ground Panels
Ground panels are absolutely the most efficient means of capturing solar. This is because you can tilt the panel and turn the panel to meet the sun at a 90 degree angle.
Roof mounted panels are far less efficient because you cannot adjust the angle of the tilt or turn.
A 200 watt solar panel on the ground, tilted and turned at a 90 degree angle to the sun will deliver its full 200 watts. However, the same roof mounted panel will deliver far less, anywhere from 50 watts to 100 watts.
- Ground panels require much more “babysitting” to constantly adjust to the sun throughout the day.
- You cannot set up ground panels while overnighting at a Walmart or rest area.
- Ground panels cannot be used while “stealth camping” in an urban area.
- Ground panels have the advantage of letting you park your RV in the shade, while placing the panel in the sun.
- Roof mounted panels will continue to charge your batteries even while driving down the road.
Most boondockers go with roof mounted panels despite the pros and cons of each. Some boondockers will also add a few ground panels to compliment their roof panels.
Don’t Forget the Solar Charge Controller
All solar panels must be wired into a solar charge controller. The controller is then wired into your battery bank. The purpose of the controller is to turn off charging once batteries are full. Otherwise, if batteries continue to charge, they will get hot and eventually catch on fire.
Solar charge controllers are often thought of as the “Achilles Heel” of solar and battery systems. This is because most RV manufacturers and shops install very cheap controllers to help bring cost down.
A cheap controller is not programmable. Probably 80 to 90% of the controllers sold on Amazon, Walmart, and Camping World can be considered “cheap controllers”. These controllers assumes you are running a typical solar array at 12 volts, and assumes you are using a typical battery bank with a bulk charge rate of 14.4 volts, and won’t allow you to run anything else.
- Victron solar charge controllers (see it on Amazon) are by far and away the most popular and most respected brand among boondockers. They are fully programmable and can be monitored (and programmed) via Bluetooth from your cellphone.
You Will Need an Inverter Too
An inverter will convert battery power (DC) into 110 volt (AC) power. Air conditioning units will require 110 volt AC power. When you consider a 15,000 BTU air conditioning unit needs about 3,500 watts of power just to start up, you will need at least a 5,000 watt inverter. The reason is because inverters will convert DC to AC power with a 85% efficiency. So, a 4,000 watt inverter will realistically deliver 3,400 watts. Meanwhile, a 5,000 watt inverter will deliver about 4,250 watts.