How Many Solar Panels & Batteries to Run a Window Air Conditioner?

Switching to solar can offset your energy bill by between 15 to 25%. Heating and air conditioning make up 40% of your energy bill. These two are the biggest contributors to energy demands in a building.

As they need so much electricity to run, it is only natural to wonder if you can operate an air conditioner or heating on solar panels.

How many solar panels do I need for a 5000 BTU air conditioner?

A 5000 BTU (British Thermal Units) air conditioner requires between 400 to 600 watts of solar energy to run for 7-8 hours. That is two or three solar panels at most, depending on the rated watt capacity of each solar panel. For example, 375-watt and 225-watt solar panels could be used to supply the total energy requirement.

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In this article, we will look at whether you can run an air conditioner on solar panels. We’ll look into how many solar panels and batteries you would need to power a 5000 BTU air conditioner. Finally, we will examine whether you can run an air conditioner with a 100-watt solar panel.

Can You Run a Window Air Conditioner on Solar Panels?

Air conditioners, like any other electrical appliance, can be run on solar panels. It is possible to easily use solar panels to power the air conditioner if enough solar panels are available to supply the required amount of energy the air conditioner needs to run.

Depending on how often you use it and the size of your building, air conditioning can cost anywhere between $150 to $300 every year. That is between 6 to 12% of your energy bill. That is quite a hefty bill you can save by powering your AC unit with solar.

For more on this, check out our post titled Can Solar Panels Run an Air Conditioner? All You Need To Know!

How to Power an Air Conditioner Using Solar Panels?

Three main types of air conditioners use solar.

  1. Solar photovoltaic air conditioners are the most common. These work like any other appliance. Solar panels mounted on the roof capture and convert sunlight to electricity that powers the AC unit.
  2. Solar thermal air conditioners use a plate to absorb solar energy. The energy goes to the compressor that generates the cool air in the air conditioner. Solar thermal AC units are less efficient than solar photovoltaic air conditioners so they are not the best option if you are looking to save on energy.
  3. Absorption chillers use evaporation and condensation to generate cool air. Solar panels power the fan and compressor of the unit.

All of these systems can be run directly with solar panels and with a battery as well. A useful fallback is to also have them connected to the grid. This ensures the air conditioner still has power on cloudy days when there is not enough solar energy.

For more on your solar panel settings, check out our post ” Can Solar Panels Work without A Battery? All You Need To Know!

How Effective Is a Solar-Powered Air Conditioner?

An air conditioner running on solar panels will work just as well as an air conditioner running on utility-supplied electricity. It will still supply cool air at the same rate. The only difference is it will be a lot cheaper since you are using solar.

These numbers are a rough but fairly accurate estimate. The exact number would depend mostly on the air conditioner’s energy consumption and the amount of sunlight the solar panels receive.

Calculating Energy consumption

Working out the energy consumption of appliances like laptops or stereos is simple because they draw a constant current. For appliances like refrigerators and air conditioners, it is a little more complicated because they draw an intermittent current.

Ordinarily to work out the consumption of an air conditioner you would simply multiply its energy consumption by the duration of use. In practice that would look like this for a 450-watt air conditioner running for 8 hours:

450 watts x 8 hours = 3600 watts

This, however, would give you an inaccurate figure. Refrigerators and air conditioners do not run the whole time they are on. Instead, they have thermostats that automatically turn off the unit as soon as the temperature cools to the required setting. When it heats up again, they switch on and run until they cool the temperature down.

This ensures they run efficiently as opposed to running 24/7. A more accurate measure of consumption uses the real consumption and not rated consumption. This is called the duty cycle or how much time as a percentage the air conditioner runs. The best way to find out the duty cycle of an appliance is with a monitoring device.

The duty cycle will depend on the outdoor temperature and your insulation. The hotter it is the more the air conditioner will have to work and thus the higher the duty cycle will be. Using a duty cycle of 70% here’s what the actual consumption will look like:

450 watts x 8 hours x 70% = 2520 watts

How Much Sunlight Will the Solar Panels Receive?

Apart from consumption you also need to factor in how much sunlight the solar panels will receive. Some areas are sunnier than others. Typically, it’s much warmer in the southwest than when you move to the north of the US. You can work out how much sun your solar panels will receive with this free tool. (Source)

Once you know your consumption and how much sunlight your solar panels receive you can easily work out the exact amount of energy you would need to run your air conditioner.

How Many Batteries Do I Need for A 5000 Btu Air Conditioner?

Two or three 12V-100-Ah lithium batteries can power an air conditioner for around 6 to 8 hours. You would need between four and six 12V-100-Ah lead-acid batteries to power your air conditioner for the same amount of time.

Lithium batteries have a deeper depth of discharge than lead-acid batteries. That is why you need fewer of them. The depth of discharge of a battery is how much energy you can safely draw from it before you need to charge it. Lithium allows you to draw up to 80% while lead-acid batteries give you 50% of usable energy. (Source)

Can a 100-Watt Solar Panel Run an Air Conditioner?

100 watts of solar energy is not enough to run an air conditioner. Standard air conditioning units use between 400-and 600 watts of energy. A 100-watt solar panel will not supply enough energy to power an appliance that consumes 400-600 watts.

You could, however wire several 100-watt solar panels together to generate enough energy to power an air conditioning unit.



I am a very well-experienced techie civil engineer who’s extensively interested in solar panel technology and even more captivated by the potential of solar panels in supporting individual residential units.

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