Window air conditioners are rated in BTU, sold on BTU, and argued about in BTU, but your electricity bill has never heard of a BTU. What the meter sees is watts. A 8,000 BTU unit that draws 700 W and a 12,000 BTU unit that draws 1,100 W will both cool a room; one of them will do it for half again as much money per hour.
A typical window air conditioner draws around 900 W while the compressor is running, which is $0.17 per hour at the US average rate of 18.44ยข per kWh. Eight hours a night comes to $1.33, and a full 30-day month of that pattern is $39.83. Small 5,000 BTU units land closer to 500 W; large 12,000 BTU units push past 1,400 W.
Calculate it for your own window air conditioner
Change any box. The result updates as you type.
Planning estimate. The rate box is prefilled with a regional average; the figure on your own bill is the one that matters. Power is draw while running, not while switched on.
| Run time | Electricity used | Cost |
|---|---|---|
| Per hour of runtime | 0.90 kWh | $0.17 |
| Per day at 8 hours | 7.20 kWh | $1.33 |
| Per week | 50.40 kWh | $9.29 |
| Per 30-day month | 216.00 kWh | $39.83 |
| Per year of that pattern | 2,628.00 kWh | $485 |
BTU is what it does. Watts is what it costs.
BTU per hour is cooling output. Watts is electrical input. The ratio between them is the efficiency rating, published as CEER on the yellow EnergyGuide label. Divide BTU by CEER and you get the running wattage, which is the number that costs money.
A 10,000 BTU unit with a CEER of 12 draws about 833 W. The same 10,000 BTU with a CEER of 9 draws about 1,111 W. Over a summer that difference is real money, and it is the only spec on the box that predicts your bill. Bigger BTU does not mean better; an oversized unit cools the room fast, switches off, and leaves the humidity behind, which is why the room feels clammy and you end up setting it colder.
| Rated power | Per hour | Per day (8 h) | Per month |
|---|---|---|---|
| 500 W | $0.09 | $0.74 | $22.13 |
| 700 W | $0.13 | $1.03 | $30.98 |
| 900 W | $0.17 | $1.33 | $39.83 |
| 1,200 W | $0.22 | $1.77 | $53.11 |
| 1,440 W | $0.27 | $2.12 | $63.73 |
The compressor is not running as much as you think
An air conditioner almost never runs continuously. The compressor cycles: it runs until the room hits the thermostat setting, shuts off, and the fan often keeps going. On a mild evening a correctly sized unit might run 30 percent of the time. During a heat wave, with the outdoor temperature above 95, it may approach 100 percent and simply never catch up.
This is why August bills shock people who did nothing different. Same unit, same thermostat setting, far more compressor hours. The table below shows what different amounts of actual compressor time cost.
| Hours per day | kWh per day | Per day | Per 30 days |
|---|---|---|---|
| 1 h | 0.90 | $0.17 | $4.98 |
| 2 h | 1.80 | $0.33 | $9.96 |
| 4 h | 3.60 | $0.66 | $19.92 |
| 6 h | 5.40 | $1.00 | $29.87 |
| 8 h | 7.20 | $1.33 | $39.83 |
| 12 h | 10.80 | $1.99 | $59.75 |
| 24 h | 21.60 | $3.98 | $119 |
What your rate does to the same unit
Cooling is a summer-peak load, and summer peak is exactly when time-of-use tariffs charge the most. If your utility bills by time of day, the rate you pay for 3pm cooling can be double the overnight rate. Our time-of-use bill calculator is the better tool if that describes your plan.
| Your rate | Per hour | Per day (8 h) | Per month | Per year |
|---|---|---|---|---|
| 10.00¢/kWh | $0.09 | $0.72 | $21.60 | $263 |
| 13.00¢/kWh | $0.12 | $0.94 | $28.08 | $342 |
| 15.00¢/kWh | $0.14 | $1.08 | $32.40 | $394 |
| 18.44¢/kWh | $0.17 | $1.33 | $39.83 | $485 |
| 22.00¢/kWh | $0.20 | $1.58 | $47.52 | $578 |
| 26.00¢/kWh | $0.23 | $1.87 | $56.16 | $683 |
| 30.00¢/kWh | $0.27 | $2.16 | $64.80 | $788 |
| 35.00¢/kWh | $0.32 | $2.52 | $75.60 | $920 |
Window AC running cost by state
Same 900 W unit, eight hours a day, every state. Note how the Southeast and South Central states, which need the most cooling hours, mostly enjoy the lowest rates. New England has the opposite arrangement and generally needs fewer hours.
| State | Rate | Per hour | Per day | Per month |
|---|---|---|---|---|
| Alabama | 16.77¢ | $0.15 | $1.21 | $36.22 |
| Alaska | 28.23¢ | $0.25 | $2.03 | $60.98 |
| Arizona | 15.23¢ | $0.14 | $1.10 | $32.90 |
| Arkansas | 14.36¢ | $0.13 | $1.03 | $31.02 |
| California | 33.25¢ | $0.30 | $2.39 | $71.82 |
| Colorado | 16.16¢ | $0.15 | $1.16 | $34.91 |
| Connecticut | 27.37¢ | $0.25 | $1.97 | $59.12 |
| Delaware | 19.38¢ | $0.17 | $1.40 | $41.86 |
| District of Columbia | 25.40¢ | $0.23 | $1.83 | $54.86 |
| Florida | 15.17¢ | $0.14 | $1.09 | $32.77 |
| Georgia | 15.84¢ | $0.14 | $1.14 | $34.21 |
| Hawaii | 52.00¢ | $0.47 | $3.74 | $112 |
| Idaho | 12.35¢ | $0.11 | $0.89 | $26.68 |
| Illinois | 23.85¢ | $0.21 | $1.72 | $51.52 |
| Indiana | 18.15¢ | $0.16 | $1.31 | $39.20 |
| Iowa | 14.14¢ | $0.13 | $1.02 | $30.54 |
| Kansas | 15.13¢ | $0.14 | $1.09 | $32.68 |
| Kentucky | 14.98¢ | $0.13 | $1.08 | $32.36 |
| Louisiana | 14.15¢ | $0.13 | $1.02 | $30.56 |
| Maine | 28.63¢ | $0.26 | $2.06 | $61.84 |
| Maryland | 21.77¢ | $0.20 | $1.57 | $47.02 |
| Massachusetts | 28.82¢ | $0.26 | $2.08 | $62.25 |
| Michigan | 22.01¢ | $0.20 | $1.58 | $47.54 |
| Minnesota | 16.95¢ | $0.15 | $1.22 | $36.61 |
| Mississippi | 16.16¢ | $0.15 | $1.16 | $34.91 |
| Missouri | 13.68¢ | $0.12 | $0.98 | $29.55 |
| Montana | 14.67¢ | $0.13 | $1.06 | $31.69 |
| Nebraska | 13.59¢ | $0.12 | $0.98 | $29.35 |
| Nevada | 13.60¢ | $0.12 | $0.98 | $29.38 |
| New Hampshire | 27.33¢ | $0.25 | $1.97 | $59.03 |
| New Jersey | 23.27¢ | $0.21 | $1.68 | $50.26 |
| New Mexico | 14.12¢ | $0.13 | $1.02 | $30.50 |
| New York | 29.93¢ | $0.27 | $2.15 | $64.65 |
| North Carolina | 15.09¢ | $0.14 | $1.09 | $32.59 |
| North Dakota | 13.61¢ | $0.12 | $0.98 | $29.40 |
| Ohio | 19.52¢ | $0.18 | $1.41 | $42.16 |
| Oklahoma | 13.38¢ | $0.12 | $0.96 | $28.90 |
| Oregon | 16.27¢ | $0.15 | $1.17 | $35.14 |
| Pennsylvania | 21.55¢ | $0.19 | $1.55 | $46.55 |
| Rhode Island | 29.46¢ | $0.27 | $2.12 | $63.63 |
| South Carolina | 16.18¢ | $0.15 | $1.16 | $34.95 |
| South Dakota | 15.73¢ | $0.14 | $1.13 | $33.98 |
| Tennessee | 14.47¢ | $0.13 | $1.04 | $31.26 |
| Texas | 16.44¢ | $0.15 | $1.18 | $35.51 |
| Utah | 12.96¢ | $0.12 | $0.93 | $27.99 |
| Vermont | 24.89¢ | $0.22 | $1.79 | $53.76 |
| Virginia | 17.61¢ | $0.16 | $1.27 | $38.04 |
| Washington | 14.95¢ | $0.13 | $1.08 | $32.29 |
| West Virginia | 16.80¢ | $0.15 | $1.21 | $36.29 |
| Wisconsin | 19.74¢ | $0.18 | $1.42 | $42.64 |
| Wyoming | 14.80¢ | $0.13 | $1.07 | $31.97 |
Six ways to cut the cooling bill
Things that meaningfully reduce the number:
- Raise the setpoint before you do anything else. Each degree warmer cuts compressor runtime, and runtime is the whole cost. Going from 70 to 74 often cuts cooling energy by a fifth or more.
- Seal the window kit properly. Those accordion side panels leak badly. Foam board and weatherstrip tape around the unit costs a few dollars and directly reduces run hours.
- Clean the filter monthly during the season. A clogged filter starves airflow, which extends every cycle.
- Use a fan with it. A $0.01-per-hour ceiling fan lets most people sit comfortably two or three degrees warmer, and the fan draws roughly one fifteenth of what the compressor does.
- Shade the window. Direct sun on the room is load the compressor has to remove. Blinds closed during the day is free.
- Do not run it in an empty room on a timer to have it cool when you arrive. Pre-cooling a room for an hour costs more than the ten minutes it takes to cool once you are in it.
Window unit versus central air
A window unit uses roughly a quarter of what central air uses, because it is cooling one room instead of an entire house and has no duct losses. If you only occupy one or two rooms for most of the day, running window units and leaving the central system off is usually cheaper, sometimes dramatically.
That flips once you are running three or four of them. At that point a properly sized central system or a mini-split is more efficient per unit of cooling, and a mini-split has the additional advantage of working as a heat pump in winter. The cooling cost calculator handles that comparison with your own numbers.
How this compares to everything else you plug in
Cost per hour of runtime for everything people use to stay cool. The gap between a ceiling fan and a compressor is the reason fans are worth running alongside the AC rather than instead of it.
| Appliance | Typical power | Cost per hour |
|---|---|---|
| Window air conditioner | 900 W | $0.17 |
| Portable air conditioner | 1,100 W | $0.20 |
| Central air conditioner | 3,500 W | $0.65 |
| Mini-split heat pump | 900 W | $0.17 |
| Ceiling fan | 60 W | $0.01 |
| Box fan | 75 W | $0.01 |
Questions people actually ask
How much does it cost to run a window AC for 8 hours?
How many watts does a window air conditioner use?
Is it cheaper to run a window AC or central air?
Does turning the AC off when I leave save money?
Do window ACs use a lot of electricity on fan-only mode?
Does a higher BTU unit cost more to run?
Related running costs
Running it on solar
A window air conditioner uses 7.20 kWh a day, which needs about 5 standard 400 W panels. Full array, battery and inverter sizing is on how many solar panels to run a window air conditioner.
Run the numbers on your own bill
- Air Conditioner and Heat Pump Cooling Cost Calculator
- Time-of-Use Electricity Bill Calculator
- Electricity Cost Calculator
Costs on this page use a national average residential rate of 18.44¢ per kWh (August 2026, EIA-derived state residential averages). Your own rate is printed on your electricity bill and is the number that actually matters. Every figure here is recalculated from one central rate setting, so these tables move when the national average moves.