How much electricity does an air conditioner use?
A window air conditioner of the usual size — 8,000 to 12,000 BTU an hour — uses **426 kWh a year**. That is the median of 201 certified models, and the middle half fall between 400 and 500. At the US average tariff that is about **$79 a year**. But of all the appliances on this site, this is the one where the annual figure is least likely to match your bill, and the reason is worth reading.
Work it out with your own tariff
Your rate, cents per kWh
There is no hours setting here, unlike the other device pages. This appliance is not certified in watts at all — only as a yearly total, and that total already includes a defined pattern of use. Multiplying it by hours of your own would count the usage twice.
| Period | Cost | Where it comes from |
|---|---|---|
| A year | $128 | 426 kWh — the measured figure |
| A month | $11 | a twelfth of the year |
| A day | $0.35 | a 365th of the year |
426 kWh × 30¢ = $128 a year. That averages 49 W drawn continuously.
426 kWh a year is the median of 201 certified room air conditioners rated 8,000 to 12,000 BTU per hour; the middle half fall between 400 and 500. Measured under the DOE federal test procedure, which assumes a defined cooling season. Watts are not published for this appliance at all. Rate defaults to 18.44¢ (U.S. Energy Information Administration, 2026-05) — a national average, which is wrong for you specifically, so put your own in above.
By cooling capacity
| Cooling capacity | Middle half | Median | Models measured |
|---|---|---|---|
| 5,000-8,000 BTU/h | 274-328 kWh | 328 kWh | 41 |
| 8,000-12,000 BTU/h | 400-500 kWh | 426 kWh | 201 |
| 12,000 BTU/h and up | 600-900 kWh | 656 kWh | 221 |
A large unit uses roughly twice what a small one does — but a unit too small for the room runs continuously and can cost more than a correctly sized larger one. Capacity is not the same as consumption.
The yearly figure assumes a cooling season, and yours is different
Every other appliance on this site runs all year. An air conditioner does not, and the certified annual figure embeds an assumed number of cooling hours — a national average of climate and use.
If you are in Phoenix running it five months a year, the label understates your cost badly. If you are in Seattle using it three weeks in August, it overstates it by a large multiple. The gap here is not a rounding difference; it can be threefold in either direction.
This is why the figure is presented as measured-under-a-defined-season rather than as your annual cost, and why there is no hours setting on this page: adding your own hours on top of a figure that already contains a season would count the cooling twice.
Per month, during the season
Divided by twelve, 426 kWh is 35.5 kWh a month — but that is a twelfth of a year, not a month of use. Spread over a four-month cooling season instead, the same total is about 107 kWh a month, roughly $20.
Both numbers come from the same measurement, and neither is wrong. Which one answers your question depends on whether you want the yearly cost spread evenly or the cost while it is actually running. Pages quoting one monthly figure rarely say which they mean.
What it costs you specifically
Set your own tariff below.
What this does not account for
The assumed cooling season is the biggest source of error on this page. The federal test procedure fixes cooling hours at a national average. Your climate can move the real figure severalfold in either direction, and unlike the hours on the television page, this assumption is inside the measurement and cannot be adjusted without discarding it.
Room size and unit sizing change the answer. An undersized unit in a large room runs constantly. An oversized one cycles inefficiently and dehumidifies poorly. The certified figure assumes the unit is appropriately matched to its space.
These are window and room units, not central air or mini-splits. Central systems are certified on a completely different basis (SEER ratings against a whole-house load) and their figures are not comparable to these.
Certified units are a biased sample. Certification is voluntary and efficient models earn it. An older window unit uses more.
Sources
- 01ENERGY STAR certified room air conditioners — measured annual energy useU.S. Environmental Protection Agency ·
- 02Electric Power Monthly, Table 5.3 — average price of electricity to ultimate customersU.S. Energy Information Administration ·
How these figures are produced: see our methodology.
Figures are calculated from published wattages and a published tariff, both dated above. They are good for comparing devices, not for predicting your bill: your rate, settings and usage all differ.