Off-grid camping is one of the finer things in life. Peace, nature, outdoor cooking… everything seems alright while boondocking. But suddenly, the heat of the day starts to wear at you. You try to find refuge in your RV, but it’s even hotter than the outdoors. You fire up the generator to power that AC unit, but now your peace and quiet is ruined—if only we had solar power, you think, as you doze off to the drone of the generator.
Can I Run My RV Air Conditioner on Solar Power?
The short answer is yes, you can run your RV air conditioner using solar power. Technically, you can power just about anything using solar power (many houses are run exclusively on solar power), but with an RV, there are a few limiting factors. These include the interior space needed for storing batteries, as well as the roof size for mounting solar panels.
The long answer is a bit more complicated, but it just requires a few calculations to accurately determine the battery power and number of solar panels that you will require.
How to Calculate Solar Power Requirements for RV Air Conditioner
There are a few simple steps to take to determine if a solar-powered RV air conditioner is feasible for you.
- First, we will find the wattage of the air conditioner and convert that to watt hours (wH).
- Then, we will determine the battery capacity necessary to support the AC unit.
- Next, we will find a power inverter that can convert the 12V battery power to the 120V that the AC unit expects.
- Finally, we can calculate the number of solar panels necessary to support the AC unit and determine if it is feasible for the size of our RV.
Let’s get to it!
How Many Watts Does an RV Air Conditioner Use?
The output power of air conditioners is usually measured in BTUs (British Thermal Unit). The standard RV air conditioner puts out 13500 BTUs, which is enough to cool a space of around 500 sq. ft.
The Coleman Mach 3 Plus is a popular RV air conditioner—we will use it for our example calculations today. By doing a quick Google search, we are able to determine that the Coleman requires 1560W @ 120V. The wattage for your air conditioner should be readily available in the manual or online.
We will make a few generalizations and assumptions as we move through our calculations, so your exact numbers may differ depending on your needs. We will assume that the air conditioner is only being run during the hottest part of the day, which equates to around 5 hours each day.
Sizing the Battery Bank
To help size our inverter, battery bank, and solar panels, we will need to know the watt hours that the air conditioner will draw. The calculation for wH is simple:
- watts x hours = watt hours (wH)
For our Coleman unit, we will multiply 1560 watts by 5 hours to find that it will draw 7800wH of power each day. Not only will we need enough solar panels to gather this power, but also the battery capacity to store and supply it.
To determine our battery capacity requirements, we will start by converting watt hours to amp hours (aH) using this equation:
- watt hours / voltage = amp hours
RV batteries are usually a 12V system, and aH is the universal standard for measuring battery capacity. So, our calculation for the battery capacity needed to support the Coleman unit will be:
- 7800wH / 12V = 650aH
However, there is one more idea to consider: RV batteries should never be drained to empty, or you risk damaging the battery or drastically reducing its lifespan. Lead acid batteries should not be drained below 50% capacity, so you will actually need 1300aH (650aH x 2) to support the Coleman AC unit.
Lithium batteries are a newer technology and can be safely drained to 0, so you would only need 650aH to support the air conditioner. Lithium batteries are much lighter and last longer, but they come at a higher price point.
These calculations are for the air conditioner alone, so you will need more battery capacity if you plan to power other appliances.
Power Inverter for RV Air Conditioner
So, now you have your 12V battery system sized up, but the air conditioner is asking for 120V power—that’s where the power inverter comes into play.
A power inverter turns that 12V power into 120V that your AC unit can digest. Finding an inverter is simple, as it just needs to be rated for at least the amount of power that will be running through it. In our case, a 2000W power inverter should handle the job with ease.
How Many Solar Panels to Power AC Unit?
Now that we have all of our power requirements, we can figure out the amount of solar panels needed to supply that wattage. Solar panels gather the most power in the summer when the sun is out the longest. Since we are powering an AC unit, we will assume that you have at least 5 hours of summer sun each day.
We will use another simple equation here to determine the solar panel wattage that our system requires:
- wH requirements / sun hours = solar panel watts
So, in the case of our Coleman AC unit, our calculation will be as follows:
- 7800wH / 5 hours of sun = 1560W of solar panels
Now, if you have done any looking around at solar panels, you will know that 1560W of panels will require a large amount of roof space. For instance, the popular Renogy 100W flexible solar panel measures approximately 2 ft. x 4 ft., or 8 sq. ft. To supply 1560W of power, you would need 16 panels, or at least 128 sq. ft. of roof space. Smaller RVs may have trouble finding the space for this many panels.
Solar-Powered Air Conditioner: Is It Worth It?
If you have the roof space and the budget, go for it! Otherwise, you may need to rely on shore power or a generator to effectively power an RV air conditioner, as 16 solar panels and a large battery bank may not be suitable for every RV.
As an added note, our calculations above assume perfect charging conditions and no loss of power anywhere in the system. This is effectively impossible, so adding a battery and solar panel cushion of 10-20% will help mitigate this issue.
In milder climates, you may not need a full-fledged air conditioner. Roof vent fans are an effective low power RV air conditioner, as they exhaust the hot air while creating a stream of cool air throughout the RV.