How Much Electricity Does an Air Conditioner Use?
Air conditioning is the largest single use of electricity in American homes. What your own unit costs depends on its size, its efficiency rating and how many hours the compressor runs.
Quick answer
A room air conditioner's watts are roughly its BTU rating divided by its efficiency rating (CEER). A 10,000 BTU window unit at the ENERGY STAR minimum of 14.7 draws about 680 watts, and one rated at a CEER of 11 about 900 watts. At the U.S. average rate of 18.31 cents per kWh that is 12 to 16 cents an hour, or $30 to $40 a month at 8 hours a day.
- Difficulty
- Easy DIY
- Watts
- BTU ÷ CEER
- 10,000 BTU window unit
- About 680 to 900 W
- 900 W for 8 hours
- About $1.32
- Share of home electricity
- 19% goes to air conditioning (EIA)
On this page
According to the U.S. Energy Information Administration, air conditioning accounts for 19 percent of the electricity used in American homes, the largest share of any single use, and about 89 percent of homes had air conditioning in 2020. So it is worth knowing what your own unit draws.
Find your unit’s watts
There are two ways.
- Read the nameplate. Every air conditioner has a label, usually on the side or behind the front grille, that lists watts or amps. If it lists amps, multiply by the voltage on the same label.
- Divide BTU by CEER. The yellow EnergyGuide label on a room air conditioner shows its cooling capacity in BTU per hour and its combined energy efficiency ratio (CEER). Capacity divided by CEER gives the approximate watts.
To earn the ENERGY STAR label, a room air conditioner without a heating mode must reach at least these CEER values:
| Cooling capacity | Minimum CEER (ENERGY STAR) | Approximate watts at that rating |
|---|---|---|
| Under 6,000 BTU | 13.1 | About 380 W for 5,000 BTU |
| 6,000 to 7,999 BTU | 12.8 | About 470 W for 6,000 BTU |
| 8,000 to 10,999 BTU | 14.7 | About 680 W for 10,000 BTU |
| 11,000 to 13,999 BTU | 13.0 | About 920 W for 12,000 BTU |
| 14,000 to 19,999 BTU | 14.4 | About 970 W for 14,000 BTU |
These are the values for units with louvered sides, the common window type. A unit with a lower CEER draws more watts for the same cooling: 10,000 BTU at a CEER of 11 is about 900 watts.
The calculation
Cost per hour = watts ÷ 1,000 × your rate per kWh
A 900-watt unit uses 0.9 kWh per hour. At 18.31¢ per kWh that is 0.9 × $0.1831 = about 16 cents per hour.
Cost by wattage
Calculated at 18.31¢ per kWh, the U.S. average residential rate for July 2026. A month is 30.4 days. “Hours” means hours the compressor is actually running.
| Unit draw | Per hour | 8 hours | Month at 8 hours a day |
|---|---|---|---|
| 500 W | 9¢ | 73¢ | $22.26 |
| 680 W | 12¢ | $1.00 | $30.28 |
| 900 W | 16¢ | $1.32 | $40.08 |
| 1,200 W | 22¢ | $1.76 | $53.44 |
Electricity prices differ a great deal between states. The same 900-watt unit running 8 hours a day for a month:
| At 12¢/kWh | At 18.31¢/kWh | At 25¢/kWh | At 35¢/kWh |
|---|---|---|---|
| $26.27 | $40.08 | $54.72 | $76.61 |
Use the appliance energy cost calculator for your own watts, hours and rate.
Why real bills are often lower than the table
The compressor does not run all the time. Once the room reaches the set temperature, the compressor cycles off and only the fan runs. The hotter the day, the sunnier the room and the lower the thermostat setting, the longer the compressor runs. A plug-in electricity monitor on a 120-volt unit shows the real kWh over a day.
Central air conditioning
A central system works the same way but on a larger scale, and its outdoor unit has its own nameplate with amps and volts. Because the cost depends so heavily on the size of the system and how long it runs, the reliable way to see it is on the bill: compare a summer month with a mild month in spring or fall.
Ways to use less
- Size it correctly. An oversized unit costs more to buy and cycles on and off too often. ENERGY STAR sizes room units by floor area: 5,000 BTU for 100 to 150 square feet, up to 14,000 BTU for 550 to 700. The air conditioner size calculator does this for your room.
- Set the thermostat as high as is comfortable. ENERGY STAR suggests 78°F as a typical setting.
- Seal around a window unit. ENERGY STAR notes that an improperly installed room air conditioner leaks as much air as a six-square-inch hole.
- Use a fan with it. Moving air lets many people stay comfortable at a higher setting. A fan costs a few cents an hour.
- Keep the filter clean. A clogged filter restricts airflow and can lead to ice on the coil.
Frequently asked questions
How many watts does a window air conditioner use?
Divide the BTU rating by the CEER on the yellow EnergyGuide label. A 6,000 BTU unit at a CEER of 12.8 draws about 470 watts, a 10,000 BTU unit at 14.7 about 680 watts, and a 12,000 BTU unit at 13.0 about 920 watts. The nameplate on the unit gives the exact figure.
Does an air conditioner use a lot of electricity?
Yes, compared with almost everything else in the house. The Energy Information Administration reports that air conditioning accounts for 19 percent of the electricity used in U.S. homes, more than any other single use.
Does a portable air conditioner use more electricity than a window unit?
Read the labels and compare the watts. For the same BTU rating, the unit with the higher CEER draws fewer watts. The calculation is the same for both types: watts divided by 1,000, times hours, times your rate.
Is it cheaper to leave the air conditioner on all day?
No. An air conditioner uses electricity whenever its compressor runs, and it runs less when the thermostat is set higher or the unit is off. ENERGY STAR advises setting the thermostat as high as is comfortable, typically 78°F.
Sources
- Electricity use in homes U.S. Energy Information Administration
- Room Air Conditioners Key Product Criteria ENERGY STAR
- Room Air Conditioners ENERGY STAR
- Electric Power Monthly, Table 5.6.A: Average Price of Electricity to Ultimate Customers U.S. Energy Information Administration
First published October 8, 2026. Last reviewed October 8, 2026. Spot an error? Tell us and we will check it against the source.