Off Grid Air Conditioning And The Inverter That Powers Them


I love living off grid, generating my own power from solar.  But it comes with a price.  Instead of just plugging things in without giving it a second thought, being off grid means I have to seriously consider what electrical power load I’m asking my system to carry.

When it comes to living in a hot climate, you may one day wonder if you can have an Air Conditioner work with your off-grid system.  I know I did.  Turns out you can, as long as you have the right components to get the job done, with the size of your inverter being one of the most important.

A small window air conditioner of up to 8000 btu would require a minimum size inverter of 3000 watts in order to properly operate on an off grid solar system.  They typically use a half Kilowatt hour for every hour that they are in use, requiring additional solar panels to operate as well.

Still at a loss on where to get started? Don’t worry. In this article, we’ll go over the best inverter for air conditioners, how to calculate your AC’s power usage, and how many solar panels you’ll need to power up your AC unit successfully.


Related: The best Inverter to run an AC unit while living off grid is the Outback VFXR3524AOpens in a new tab.. You won’t regret it.


Off Grid Air Conditioners

We’ll be focusing on buying an inverter that can power a window air conditioning unit while utilizing off grid solar. Typically these units use alternating current (AC), but some use direct current (DC). 

Before purchasing an inverter, here are some questions to ask yourself about your AC unit:

  1. How many volts is the AC Unit? Typical less than 120V is the best choice.
  2. How many watts does the AC unit require? (see how to calculate this below)
  3. Is the unit big enough to cool down the area? Check how many square feet the air conditioning unit will cool down.

If you are still in the market for an AC Unit, one of the best that you can find for off grid use is the GE 8000 BTU Smart Window Air ConditionerOpens in a new tab..  Powerful enough to quickly cool a medium sized room of 350 sq ft, this air conditioner can easily fit within the power needs of most modest off grid systems.

This Inverter Will Power Almost Any Window AC Unit

There are a lot of inverters on the market, but only one that was recommend to me by Hawaiiʻs favorite Solar Specialist, Doug Mycko of SolarMan Hawaii.Opens in a new tab. The inverter he suggested is the exact one that Iʻve been using for 15 years as part of a solar system Doug installed for me and it still shows no signs of letting up.

That inverter is the Outback VFXR3524A.Opens in a new tab. This heavy-duty inverter is available in power ranges from 2000W-3600W, sufficient to power up almost any window AC unit.

As a true sine wave inverter, the energy supply to your unit will be smooth, preventing anything from overheating or overworking. It will convert up to 24VDC from your solar panels to 3500W @120VAC.

It must, however, be hooked up to a power source. If you’re off-grid, that’ll mean using your battery and/or solar panels. 

Remember, you’ll need another inverter if you’re going to power other appliances.

How To Calculate Your AC Unit’s Power Usage

If you want to know how much power your AC unit will use, first find how many amps it draws. This value should be in the owner’s manual or on the packaging.

Then multiply the number of Ampers with the number of volts of your power outlet (usually 120v or 240v). Divide the final figure by 1000 to get how much electricity your window AC unit will need in an hour.

Estimate how many hours a day you’ll be using your air conditioning unit (eight hours a day is a good rule of thumb.) Multiple the kwh by the number of hours, and you’ll have about how much energy your AC unit will consume in a day.

Check your AC unit’s energy efficiency rating to estimate how many watts the unit will consume to make BTUs.

However, other factors can impact your unit’s power usage.

  • Outside temperature. If you’re using a window AC unit, the outside temperature will affect how much energy is required to cool the air down.
  • Unit Size. Pick a unit that fits your room size. An 8000 BTU unit, for example, will cool down a 250 to 400 square foot room.
  • Humidity. High humidity will cause your AC unit to use more energy.

These Batteries Will Last Forever (almost)

When you’re living off grid, the idea is to live more lightly.  Sometimes an air conditioning unit is necessary in the hottest of climates, but does it need to be necessarily be used at night?  Maybe a couple open windows is all you need?  

But if you feel strongly about running an AC unit through the night, you’re going to need some good batteries.

You’re going to want to choose a battery pack with more kilowatt-hours than you’ll think you need. Remember, the less you drain from your batteries, the longer they’ll last. You also want to have your battery storage to keep you cool through the night.

Using lithium-ion batteries, such as the SimpliPhi Lithium Battery, is the most efficient. These are maintenance free batteries, which can hold 3.8 kWh! That almost get you through the whole night.  Great thing about these batteries, you can discharge 20-30% of full capacity.

Although they are more expensive than the alternatives, they’re rated for more cycles and will last a lot longer.

How much Power Will An AC Unit Draw From My Batteries?  

It takes a lot of energy to run an air conditioning unit, even just for an hour. 

If you’re off-grid, you’ll want to have a battery to store excess power from solar panels to power your AC even if it isn’t bright and sunny.

Using a typical window AC unit, you can estimate the use of 0 .5 Kilowatt hour per hour it runs. Depending on the size of the unit, you may have a different energy consumption, but this is a good starting point.

How Many Solar Panels Would I Want To Have For An AC Unit?

A typical window AC unit of up to 8000 btu uses up 670 watts on the low end to 1000 watts on the high end. 

There are different size solar panels. If you have 100-watt panels, you would need 7 to 10 solar panels. If you have a 250-watt panel, you would need 3 to 4. 

Remember that how much energy a solar panel produces in a day depends on how much sunlight it receives. Generally, you’ll need 6 hours of direct sunlight each day to achieve this level of wattage.

Hopefully you now have the tools you need to run an AC unit in your off grid home.  You do not have to eliminate all the comforts of life just because you are off grid.  But remember, other methods to cool your home should be employed in conjunction with the use of an AC unit.

Planting trees or building arbors that can provide shade in the right places is a great place to start when it comes to cooling your home.  Installing larger windows or doors in your home can increase airflow.  Or get a little kiddie pool and go for a dip. 

However you do it, I hope you stay cool.  Aloha

Sean Jennings

Sean has been living simply Off-Grid in Hawai'i for over 18 years. He lives debt free on Hawai'i Island with his family and over 40 chickens. When he's not tinkering around the homestead, he's off exploring the shorelines for fish & surf.

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