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Does AC cost a lot of electricity?

Mar. 07, 2024
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How Much Does Air Conditioning Cost to Run?

Air conditioning is an energy-intensive technology. It uses a lot of power to keep your home cool. But how much energy is that? It depends on a number of factors, including:

  • The size of your home
  • The size of the air conditioner
  • The temperature outside
  • The quality of your insulation

The Ideal Case

First, let’s talk about the ideal case for an air conditioner. This is the situation where the air conditioner is either brand new or works like new, is properly sized for the space, the temperatures outside aren’t too hot, and your home is well-insulated.

In this case, let’s say you’re cooling the average new single-family home in the US – about 2,400 sq feet. This requires an air conditioning unit that delivers 34,000 BTUs per hour of cooling, per the government’s Energy Star guidelines. This air conditioner will draw 2.8 kW if it has a high energy efficiency ratio (EER) of 12. HVAC professionals say that under ideal conditions, your air conditioner will actually run about 70-80% of the time, so if you have it on 24 hours a day, it will run 17-19 hours per day and consume 47-54 kWh. The average cost per kWh in the US is currently $0.11, according to the Energy Information Administration (EIA). This means an AC unit could cost you from $5.17 to $5.94 per day to run. Or about $155-$178 per month you’re running it.

Let’s say you still have an ideal home setup, but a home that’s a little bit less than the size of the average home – around 1900 square feet. Then you might have a 30,000 BTU air conditioner, which uses approximately 2.5 kW of power when it’s running. This means you’d use between 42-48 kWh and pay from $4.62 to $5.28 per day, or about $138-$158 per month.

The Role of AC Efficiency in the Cost to Run an AC Unit

In the above example, we used an air conditioner with some of the highest EER commonly found on the market today. What happens if we use an AC unit that has a lower EER, say around the average value of 8.5? The EER is defined as the ratio between the cooling an AC unit produces and the number of watts it uses. While a 34,000 BTU unit with an EER of 12 will use about 2800 watts (divide by 1000 to give the kW: 2.8), an AC unit that produces the same cooling with an EER of 8.5 will use about 4kW. Running the same amount of time per day would cause this AC unit to use 67-77 kWh and cost about $7.37 to $8.47 per day or about $221 to $254 per month.

What about our more modestly-sized house? The smaller AC unit with an EER of 8.5 would draw about 3.5 kW, use between 59 kWh and 67 kWh, and cost from $6.49 to $7.37 per day or $195 to $221 per month.

What about SEER?

If you’ve been shopping for an air conditioner recently, you have likely seen a different number measuring the efficiency of the AC unit. While we used EER, many AC manufacturers promote the SEER number.

The SEER number attempts to factor in the fact that an AC unit isn’t running all the time. By averaging the running time over the course of a range of temperatures, the hope is that this number will provide a more accurate and helpful basis for comparison between AC units. It’s hard to know if this is a more precise number or more useful, but it seems like it’s more opaque.

In truth, neither number really tells us exactly how much energy your AC unit is using, but they’re valuable estimates.

How the Cost of Electricity Affects the Cost to Run Air Conditioning

The cost to run air conditioning can vary dramatically depending on the cost of electricity in your area. Electricity rates vary widely in the US, ranging from $0.29 per kWh in Hawaii to $0.08 per kWh in Louisiana. In other words, your AC unit could cost up to four times as much to run in some places as in others.

Extreme Heat and Other Less-Than-Ideal Conditions

All our above examples assume that your air conditioner is only running about 70-80% of the time, which HVAC professionals assert is a sign that your AC unit is properly sized for your home. But this isn’t always the case. There are many things that can make your AC unit run essentially all the time. This includes:

  • Extreme heat
  • Undersized AC unit
  • Poorly maintained AC unit
  • Poor insulation

When this happens, your costs to run your AC unit will increase accordingly. Running the AC unit full-time in our big house example would cost $7.39 per day for the efficient unit, or about $222 per month. For the less efficient unit, you’re looking at $10.56 per day or about $317 per month.

Not only that, but running all day is hard on your air conditioner. AC units are not designed to run constantly, and when they do, they experience extreme wear and may develop problems. You can cut the lifespan of an AC unit in half by having it in conditions where it runs constantly.

In these conditions, your air conditioner might not even be appropriately cooling your home. It might even start blowing hot air.

AC Units Are Expensive to Run Outdoors

While AC units are expensive inside, they are even more costly to run outside. That’s because the AC unit can’t capture the cooled air and run it through the unit again, which means that the AC unit has to run constantly, and it may not cool very well because it can’t cool very much air with one pass.

In contrast, a Portacool will take in a lot of air and can drop its temperature dramatically, by perhaps as much as 30° F per pass. This makes a Portacool a much better solution for outdoor cooling.

Are you considering a portable evaporative cooler to help you beat the heat efficiently? Please visit a local or online retailer. Or you can use our online form for detailed questions or to make a bulk order.

By plugging some basic info about your AC unit and usage into a few simple formulas, you can calculate the cost of running AC.

Energy Efficiency Ratio (EER) Formula

An AC unit’s Energy Efficiency Ratio (EER) is a measure of how efficiently it uses electricity to cool a home at any given moment. You can calculate the EER of your unit by dividing its cooling output in British Thermal Units (BTUs) by the power it’s using in watts. You’ll find these numbers in the unit’s manual or printed directly on the unit. Here’s the formula:

EER = unit BTUs / Watts consumed

Seasonal Energy Efficiency Ratio (SEER) Formula

Like EER, an AC unit’s Seasonal Energy Efficiency Ratio (SEER) rating is another measure of its efficiency. However, you’ll see SEER ratings are more common than EER and are often advertised by the manufacturers of AC units. This is because SEER ratings provide a broader picture of a unit’s efficiency, taking into account its performance over the entire cooling season.

Calculate your unit’s SEER rating by dividing its total cooling output in BTUs over a season by its total energy consumption in watt hours (Wh) over the same period. Here’s the formula:

SEER = unit BTUs / Wh consumed

Cost per Hour Formula (Most Popular)

To calculate the cost to run an air conditioner for one hour, consider the unit’s wattage, the average cost of electricity in your state and the number of hours your unit runs daily. Here’s the formula:

Cost per hour = (unit wattage x average cost per kWh) / 1,000

Note: These formulas provide estimates and may not reflect the exact cost of running your air conditioning unit. Actual prices can vary depending on various factors, including the size of your home, the temperature outside and your usage habits.

Using the formula above, you can calculate the cost of running your air conditioner per hour with data from your energy bill.

For example, the average price of electricity in the U.S. was about $0.15 per kWh as of August 2023 according to the U.S. Energy Information Administration. Assuming a typical AC unit with a wattage of 1,500, the calculation would be (1,500W x $0.15) / 1,000 = $0.23 per hour. The cost to run the same AC unit may vary depending on energy prices where you live.

Per Month Costs

You can use a similar formula to estimate the monthly cost to run your AC:

Cost per month = (unit wattage x hours of use per day x days of use per month x cost per kWh) / 1,000

Using the same figures from the example above, the calculation would be (1,500W x 8 hours x 30 days x $0.15) / 1,000 = $54 per month.

Per Year Costs

To estimate how much it costs per year for you to run your AC, use this formula:

Cost per year = (unit wattage x hours of use per day x days of use per year x cost per kWh) / 1,000

Using the same figures again, the calculation would be (1,500W x 8 hours x 180 days x $0.15) / 1,000 = $324 per year. This calculation accounts for six months of use each year, but households in some areas may use their ACs more or less often.

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