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The True Cost of an Air Conditioner

Ever wonder the true cost of running your air conditioner and how it affects your utility bill? We will dive into how much kilowatt hours (kWh) an average air conditioner will use and how many solar panels would be required to offset that usage. Follow along with the calculations below to estimate how many panels you would need! Solar power will allow you to blast that cool AC throughout the summer while keeping your energy bill down.

How Much Does it Cost to Run an Air Conditioner?

The cost of running an air conditioner will vary depending on a few factors. The main factors that will contribute to the difference are: the price per kWh you pay, how often you use your air conditioner, and the size of the air conditioner. You will be able to find your current cost per kWh on a recent utility bill. If you do not have one handy you can google your utility rates in your area and get a fairly accurate number. To find out how much power your air conditioner draws, check the side of the unit. This number will be listed in watts (W). The average central air conditioner will draw close to 3,500W. If you cannot find the watts on the unit, you can google the model number or check any buyers guide you may have still. For example, if a homeowner’s A/C wattage is 3,500W, they use it for 8 hours, and pay $0.14 a kWh.

(3,500W x 8) divided by 1000 = 28 kWh 28 kWh multiply by $0.14 = $3.92

A/C Wattage x # of Hours in Use) divided by 1000 = kWh Usage for Hours in Use

kWh Usage for Hours in Use x Your Utility Rate = Cost for Hours in Use

This means the air conditioner uses 28 kWh per day and costs $3.92 per day to use. In this example if you ran it for a month it would cost on average $119.25. This number will vary depending on how many hours/ days you the air conditioner is in use, but this is a good estimate.

How Many Solar Panels Would it Require?

Determining how many panels it would take to run just an air conditioner will again vary on a few factors. Location, and panel wattage will be some of the major determining factors that will affect the production estimates. First, you will need to estimate how much your air conditioner will use annually, this number can vary year to year and for different regions. In the Midwest or a state with traditional 4 seasons, an air conditioner won't be used the entire year. For the calculation below we used 90 days, which is an estimated number of days an A/C unit is used per year. From the example above we have estimated it will use an average 2,520 kWh annually.

28kWh multiply by 90 days = 2,520kWh

To account for different regions, take the average annual kWh usage from above (2,520) and divide that by your region’s production ratio.

By doing this we will get a more accurate kWh that we will need to generate. A higher production ratio such as in California (1.6) will require less watts because that region receives more sunshine. A production ratio just helps us get a slighter more accurate number, because it takes into account a region's average number of days of sunlight.

Continuing the example above we chose a Midwest state with a 1.2 production ratio. We will need to produce roughly 2,100 kWh to offset the air conditioner usage.

2,520 kWh divided by 1.2 = 2,100 kWh

Estimated Watts Needed (kWh) / Production Ratio = Watts Needed for A/C

From there you will divide that number with the watts of the solar panels you are considering. The higher number of watts the less panels your system will require. Today’s standard 60 cell panel watts is around 320W-370W. To offset the air conditioner usage from this example we would need around 6 solar panels.

2,100kWh divided by 350W = 6 panels

Additional Watts Needed / Watts Per Panel = Number of Panels Needed

Similar to finding the additional panels needed to run an air conditioner, you can find an estimated number of panels you need for all your usage. If you add up your kWh usage for each month and divide that by the panel wattage you can get a rough estimate of how many panels you might need.


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