Multiply the air conditioner's watts by the hours it runs, divide by 1,000 to get kWh, then multiply by your price per kWh. At the 2024 US average of 16.48¢ per kWh, an 8,000 BTU window unit drawing about 660 W costs about 11¢ an hour, and a 3-ton central system drawing about 3,500 W costs about 58¢ an hour.
Key facts
- Cost = watts × hours ÷ 1,000 × price per kWh.
- EIA: the average US residential electricity price was 16.48¢ per kWh in 2024 (annual average).
- A room AC's running watts are roughly its BTU rating divided by its CEER efficiency rating.
- Air conditioning was the largest single use of household electricity in EIA's 2020 survey, at 19%.
- ENERGY STAR suggests setting the thermostat as high as is comfortable, typically 78°F.
How do you calculate the cost to run an air conditioner?
You need three numbers: how many watts the AC draws while running, how many hours the compressor actually runs, and what you pay per kilowatt-hour.
Cost = watts × hours ÷ 1,000 × price per kWh
For example, a 660 W window unit running 5 hours at 16.48¢ per kWh: 660 × 5 ÷ 1,000 = 3.3 kWh, and 3.3 × $0.1648 = about 54¢.
Two things trip people up. First, the compressor cycles on and off once the room reaches the thermostat setting, so "on for 8 hours" usually means fewer hours of full power. Second, the price on your bill may differ from the national average. The electricity cost calculator handles both and can use your state's average rate.
How many watts does an air conditioner use?
A room air conditioner's efficiency is rated as CEER, the BTU per hour of cooling it delivers for each watt. Dividing the BTU rating by the CEER gives an approximate running wattage. The table uses two CEER levels: the federal minimum that applied from 2014 until May 2026 (roughly what an older or basic unit uses) and the ENERGY STAR Version 5 minimum. Costs use the 2024 US average of 16.48¢ per kWh.
| Room AC size | Watts, older/basic unit | Cost per hour | Watts, ENERGY STAR | Cost per hour |
|---|---|---|---|---|
| 6,000 BTU | 545 W | 9¢ | 438 W | 7¢ |
| 8,000 BTU | 734 W | 12¢ | 544 W | 9¢ |
| 10,000 BTU | 917 W | 15¢ | 680 W | 11¢ |
| 12,000 BTU | 1,101 W | 18¢ | 816 W | 13¢ |
| 14,000 BTU | 1,308 W | 22¢ | 972 W | 16¢ |
| 18,000 BTU | 1,682 W | 28¢ | 1,250 W | 21¢ |
| 24,000 BTU | 2,553 W | 42¢ | 1,890 W | 31¢ |
These wattages are calculated from the efficiency ratings, not measured, and CEER also counts standby power, so treat them as estimates. Your unit's label or spec sheet gives its actual watts or amps. Units made from May 26, 2026 must meet a higher federal minimum (16.0 CEER for 8,000–13,999 BTU window units), so new models use less still. For more detail, see window AC watts and portable AC watts; a typical 10,000 BTU portable unit draws about 1,125 W, or about 19¢ an hour.
A typical 3-ton central air conditioner draws about 3,500 W while running, counting the outdoor unit and indoor blower, and roughly 2,000–6,000 W across 2- to 5-ton systems.
How much does it cost to run an AC per hour, day and month?
Window air conditioner
Take an 8,000 BTU window unit at 660 W, used 8 hours a day with the compressor running about 60% of that time on a warm day:
- Per hour of compressor running: 0.66 kWh × $0.1648 = about 11¢
- Per day: 660 W × 8 h × 0.6 = 3.2 kWh, or about 52¢
- Per month (30 days like that): about 95 kWh, or about $15.66
A 12,000 BTU ENERGY STAR unit at about 816 W, used the same way, comes to about 3.9 kWh a day: roughly 65¢ a day and $19.36 a month.
Central air conditioner
A 3-ton central system at about 3,500 W:
- Per hour of running: 3.5 kWh × $0.1648 = about 58¢
- Per hot day, running about 35% of 24 hours: 29.4 kWh, or about $4.85
- Per month of hot days (30 days): 882 kWh, or about $145
Mild days cost much less, because the compressor runs fewer hours. A month of hot days uses about as much electricity as the 863 kWh the average US home used in a whole month in 2024, which is why summer bills jump in hot states.
How much does it cost to run an air conditioner in my state?
Electricity prices vary widely by state. The table below uses EIA's 2024 annual average residential prices with the same examples as above: a 3-ton central AC on a hot day (29.4 kWh) and an 8,000 BTU window unit for a month (95 kWh).
| State | 2024 avg price | Central AC, hot day | Central AC, 30 hot days | Window AC, month |
|---|---|---|---|---|
| US average | 16.48¢ | $4.85 | $145 | $15.66 |
| California | 31.97¢ | $9.40 | $282 | $30.38 |
| New York | 24.43¢ | $7.18 | $215 | $23.22 |
| Arizona | 14.91¢ | $4.38 | $132 | $14.17 |
| Texas | 14.94¢ | $4.39 | $132 | $14.20 |
| Florida | 14.14¢ | $4.16 | $125 | $13.44 |
| Louisiana | 11.73¢ | $3.45 | $103 | $11.15 |
These are 2024 annual averages: EIA's total residential revenue divided by kWh sold, so they fold in fixed charges but not most taxes, and they smooth out seasonal and time-of-use differences. Prices have risen since; EIA's Short-Term Energy Outlook projects a higher US average for 2026. For the most accurate figure, divide your last bill's total by its kWh. See all states on the electricity rates by state page.
How can I lower the cost of running my AC?
Tips from ENERGY STAR:
- Raise the thermostat. Set it as high as is comfortable, typically 78°F. Keep lamps and TVs away from the thermostat; their heat makes the AC run longer.
- Use a fan with it. An extra fan spreads cooled air around the room. A ceiling fan uses about 50 W, a small fraction of the AC.
- Seal the window unit. Use the insulation panels that come with it. ENERGY STAR says a poorly installed room AC can leak as much air as a 6-square-inch hole.
- Run the fan on low on humid days. Slower airflow takes more moisture out of the air.
- Check filters monthly. Replace a dirty central system filter, and at least every 3 months.
- Seal and insulate ducts. ENERGY STAR says this can improve heating and cooling efficiency by as much as 20%.
- Get a yearly tune-up of a central system, and consider an ENERGY STAR smart thermostat, which ENERGY STAR says can save about $100 a year in homes with high heating and cooling bills.
- Buy the right size and efficiency. A higher CEER means fewer watts for the same cooling, and an oversized unit wastes energy. See what size air conditioner you need.
If BTU, tons and watts are confusing, what is a BTU explains the conversions.
Questions people ask
How much electricity does an AC use?
A window unit uses roughly 440–1,200 W depending on size, and a 3-ton central system about 3,500 W while running. Multiply by hours of compressor run time and divide by 1,000 to get kWh.
How many kWh does an AC use per day?
About 3.2 kWh for an 8,000 BTU window unit used 8 hours on a warm day, and about 29 kWh for a 3-ton central system on a hot day.
Is it cheaper to run a window AC or central air?
Cooling one room with a window unit uses far less electricity than cooling a whole house with central air. Per BTU of cooling, it depends on each unit's efficiency rating.
Does turning the AC up to 78°F save money?
Yes. A higher setting means the compressor runs fewer hours, and ENERGY STAR suggests setting the thermostat as high as is comfortable, typically 78°F.
What electricity price should I use?
Use the price on your own bill if you can. Otherwise, EIA's 2024 averages are 16.48¢ per kWh nationally and range from about 11.5¢ to over 40¢ by state.
Sources
- EIA: Electric Power Annual, Table 2.10, average price of electricity by state, 2024 and 2023
- EIA: 2024 average monthly bill, residential (Table 5a)
- EIA: Short-Term Energy Outlook, electricity
- EIA: Electricity use in homes
- ENERGY STAR: Room air conditioners
- ENERGY STAR: Heating and cooling
- eCFR: 10 CFR 430.32, energy conservation standards (room air conditioners)
- ENERGY STAR: Version 5.0 Room Air Conditioners Final Draft Specification
