How Many Watts Does An Air Conditioner Use? (2024)

It takes 2,365 kWh of electricity per year to cool an average home in the U.S., according to an EnergySage analysis of a Department of Energy building database. That’s enough electricity to run four full-size refrigerators all year, or keep a Tesla Model 3 rolling for about 6,500 miles.

That number varies widely depending on a handful of factors. A large (or poorly insulated) house in Phoenix, for example, could use 12,340 kWh per year for air conditioning.

On the other hand, an efficient apartment in San Francisco might only use 375 kWh (if it even uses central cooling at all).

What about the amount of energy an AC uses at any given moment? That can range from a few hundred to a few thousand watts, depending on the size of the system and some other factors.

So what should you expect in your home? Here are a few ways to make a quick estimate for an AC’s energy use.

Broadly speaking, the amount of energy you’ll need to run an air conditioner depends on your climate, your building, your comfort preferences, and the equipment itself.

• Local climate: Warmer weather means more energy for cooling. High humidity can play a role, too. Look up your climate zone on the 2021 IECC map below, or on the IECC website.

• Home size: Bigger homes generally use more energy for heating and cooling.

• Home layout: Finished basem*nts don’t need much cooling. Box-shaped buildings are more efficient than sprawling estates.

• Home weatherization: Better insulation and fewer air leaks help save energy.

• Existing HVAC: Leaky or undersized ductwork can drive up your energy costs. Ductless cooling can be exceptionally energy efficient.

• Thermostat setpoint: Every degree you turn up your thermostat tends to use 3% more energy.

• Efficiency rating: An AC or heat pump with a higher efficiency rating can significantly cut your energy use. Humidity can complicate things, but ratings still matter.

• Your contractor: Sloppy installation can increase your energy use (and cause comfort problems, too).

According to the Energy Information Administration (part of the U.S. DOE), about 9% of a typical household’s energy use is for cooling. But that’s going to vary wildly depending on the house, and the cost estimates will also vary depending on your local electricity prices.

Instead, you can try to estimate an AC’s energy use in your home with one of the following methods—explained in greater detail further below.

• Tally up your old cooling bills, then adjust the estimate based on your new system’s efficiency.

• Look at estimates based on similar homes, including the climate, building size, and efficiency.

• Take the efficiency rating, and do the math based on how long the AC will run. This only really works with single-speed ACs, which are steadily getting displaced by higher-performance models.

This takes a bit of work, but it’s likely to be pretty accurate. You’ll need to dig up your electric bills for last year’s cooling season, and back into an estimate from there. The trickiest part is separating out the cooling costs from the bill at large. An easy workaround is to find an electricity bill from a month when you don’t really use HVAC, and use that as a benchmark.

Try to figure out both how many kWh you used for cooling, and how much you spent in dollars for cooling, because both numbers are valuable.

If you’re trying to estimate how much energy you’ll save by upgrading to a newer, more efficient AC or heat pump, here’s what you’ll need to know:

• How efficient your current cooling equipment is. It might be on a sticker or badge somewhere on the AC or heat pump. For central cooling and ductless mini-splits, efficiency is measured by SEER (or SEER2, a newer but very similar scale). Most units currently in operation are rated somewhere between SEER 10 and SEER 14. Room ACs use slightly different ratings, but the principle is similar.

• How efficient your new heat pump will be. New models that qualify for tax credits are often much more efficient than the old equipment. Government regulations have forced all new ACs to get more efficient. With high-performance heat pumps—the kinds that can also heat your home in very cold weather—you can expect at least 16 SEER2, and possibly as high as 20 SEER2.

Take that info, and plug it into an AC energy savings calculator, like this one. That result will be pretty accurate.

Based on our analysis of data from the Department of Energy’s ResStock database, here’s how much a whole-house cooling system will tend to use, across different climates, home sizes, and home energy-efficiencies.

Whole-house cooling energy use estimates, 15 SEER (14.3 SEER2)

Notice the huge spread even within climate zones. Bigger or less-efficient homes within a climate zone often need five times as much electricity for cooling than smaller or more-efficient homes. (In parts of the country with mild summers, the spread can be even wider, since many homes use no cooling at all.)

Two notes about how we handled some of the data: In the original data set, many homes in colder climates only used partial-home cooling. It’s about 23% of the national total. We normalized it to whole-house cooling here for the sake of easy comparison. We also excluded homes that don't use cooling at all. That’s about 10% of homes in the U.S., and these are predominantly in the marine climates (3C and 4C) and the very cold climates (6, 7, and 8).

We also made energy-use estimates based on minimum-efficiency equipment, at 15 SEER (14.3 SEER2). If you opt for a higher-efficiency AC or heat pump—or stick with an older (likely less-efficient) model, here’s what the averages would look like.

How much does SEER rating affect an AC's energy use? Median by climate zone

So far, we’ve been looking at an AC’s total energy use in kilowatt-hours. For most people, kWh is the most important measurement because it lets you estimate the stuff that affects your finances: How much it'll cost to run, or how many solar panels you’d need to offset the energy use.

An air conditioner’s power draw, measured in watts or kilowatts (no hours attached) is a different measurement that tells you how much electricity it draws in a given moment. It doesn't directly affect your utility bills, but it does have some implications for the installation, and possibly your home's electrical system. (We cover that in a little more detail here—that article is about heat pump energy use, but the principles still apply.)

With certain kinds of central air conditioners—the basic, lower-cost, single-speed kind—you can actually use the wattage to estimate the annual power use, and it's very closely related to the SEER ratings.

First, you figure out the typical wattage while the AC (or heat pump) is running flat out in the middle of a cooling cycle:

Cooling wattage = Btu / SEER

(If you’re looking at a model with a SEER2 rating, multiply that number by 1.05 to get the rough equivalent in the regular SEER scale.)

Here are a few examples:

Basic, single-stage air conditioner power draw

Then, take the wattage, multiply it by the number of hours you think the AC will actively run per day, and you’ve got your daily energy use.

Daily energy use (kWh) = Cooling wattage x Hours in use

Then you can multiply that out to monthly energy use and seasonal energy use.

This isn’t super-likely to get you an accurate number, because almost nobody estimates the daily runtime very accurately. (It also doesn’t really work for inverter-driven ACs or heat pumps, because the wattage shifts constantly on those machines.) But it's one more piece of info to consider.

All you have to do is plug in your estimated energy use and multiply by the cost per kWh of electricity. The table below uses the EIA’s most current electricity prices by state as of March 2024.

Central AC annual operating costs, with median home cooling energy use, and minimum-efficiency equipment

Electricity Cost Source: EIA Electric Power Monthly, prices from October 2023

Did you know that a heat pump works just like an air conditioner in cooling mode, and can heat your home year round?

If you’re getting a new AC, you ought to consider just getting a heat pump instead. And when you shop around, you're more likely to find a competent contractor that will install a heat pump at a price that might even be less than a central AC, after incentives. The EnergySage Marketplace makes it easy to get and compare multiple quotes from vetted installers.

Image: iStock

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