How much electricity does an air conditioner use?

You don't need to guess: three numbers and a calculator are enough.

The answer in 2 lines. What an air conditioner uses depends on how much power it draws, how efficient it is and how many hours it runs. To estimate your cost: kilowatts drawn × hours of use = kWh, then kWh × the price per kWh on your utility bill. The EIA's latest national average for homes is 18.16 cents per kWh (August 2026), but rates vary a lot by state and by plan.

The first 3 steps

Find the wattage on the unit's label or in the manual (in watts; divide by 1,000 to get kilowatts). For a room unit, the yellow EnergyGuide label also shows an estimated yearly cost.
Find your price per kWh on your electric bill. If you have a time-of-use plan, note the peak and off-peak rates.
Estimate your hours: how many hours a day the unit actually runs, and how many hot days you get in a summer.

An example to see how it works (made-up numbers)

Step	Assumption	Result
Power while running	A window unit that draws about 900 watts (0.9 kW)	0.9 kWh per hour
Use	8 hours a day, 90 days a summer	720 hours
Energy	0.9 × 720	About 650 kWh
Cost	650 × $0.18 (close to the August 2026 national average)	About $117 for the summer

The wattage and hours are made up for the calculation: use your unit's numbers and your own rate. A central air system usually draws much more than one window unit, since it cools the whole home. The compressor also cycles on and off, so actual use is often below the maximum wattage times the hours. For real numbers, compare your usage on a hot day with and without AC.

What drives your usage up

A low setting: the Department of Energy says running your AC at 78°F instead of 72°F can save 6 to 18% on your cooling bill. A ceiling fan lets you raise the setting about 4°F with no loss of comfort.
Leaky ducts: DOE estimates homes lose about 20% of heated and cooled air through the duct system on average.
Dirty filters and an outdoor unit blocked by plants or debris.
Sun and leaks: open blinds on sunny windows, a door left open to a hot room.
The wrong size: too small, it runs all day; too big, it cycles on and off, uses more energy and removes less humidity.

What not to do

Comparing two units on price alone, without looking at the estimated yearly energy cost on the label.
Cooling an empty home all day: set the thermostat higher while you're out.
Turning the thermostat way down to "cool faster": the unit doesn't cool faster, it just runs longer.
Trusting a small "personal" desk cooler to cool a room: it won't.

Reading the efficiency ratings

Central air: efficiency is rated in SEER2 (seasonal) and EER2. These replaced the older SEER and EER ratings in 2023 and are measured differently, so a SEER2 number can't be compared directly with an old SEER number. The higher the rating, the less electricity for the same cooling. Federal minimums vary by region.
Window and through-the-wall units: look for the CEER rating. ENERGY STAR certified room units have to beat the federal minimum standards; see the ENERGY STAR room AC page to compare models.
Portable units that sit on the floor are usually less efficient than a window unit of the same capacity.

In your state

Electricity prices vary a lot from state to state. The EIA publishes the average residential price for each state every month in its Electric Power Monthly, Table 5.6.A: find your state in the "Residential" column. This is only an average: your bill shows your actual rate.
Many utilities offer time-of-use plans, where electricity costs more in late afternoon and evening. If you have one, running the AC earlier in the day (pre-cooling) can lower your cost.
Your utility or state may offer rebates for efficient AC units or heat pumps: check your utility's website.

Good to know

If you have a smart meter, your utility's online account often shows usage by day or hour: compare a hot day with the AC running against a mild day.
Change or clean filters regularly. DOE suggests once a month for room units during the cooling season, or as the manufacturer recommends.

In Phoenix, Tanya is surprised by her July bill. She checks her utility's online account: her AC ran almost all day at 72°F, even while she was at work. She sets it to 78°F when she's home, higher when she's out, closes the blinds on the west side and turns on the ceiling fan. Her August usage drops noticeably.

A made-up story, for illustration.

Bobby

Sources, verification, confidence

Verified on November 6, 2026, for the United States. Confidence: medium: the calculation method is solid and the August 2026 price comes from the EIA; the wattage and hours in the example are made up. Your rate is the one on your bill.