Air Conditioner Electricity Cost
Monthly running cost from BTU or watts
Duty cycle reflects how much of the time the compressor actually runs. Inverter/variable-speed units typically average 40–60% once the room is at temperature; older single-speed units cycle closer to 70–100% in hot weather.
Typical monthly cost by AC size (8h/day, 30 days, 17¢/kWh, EER 10)
| Size | Power | Monthly kWh | Monthly cost |
|---|---|---|---|
| 5,000 BTU | 500 W | 120 kWh | $20 |
| 8,000 BTU | 800 W | 192 kWh | $33 |
| 10,000 BTU | 1,000 W | 240 kWh | $41 |
| 12,000 BTU | 1,200 W | 288 kWh | $49 |
| 18,000 BTU | 1,800 W | 432 kWh | $73 |
| 24,000 BTU | 2,400 W | 576 kWh | $98 |
Full duty cycle shown — real usage with an inverter unit is often about half.
FAQ
How many watts does my AC use?
Divide BTU by EER: a 12,000 BTU unit with EER 10 draws about 1,200 W. Check the nameplate or the EnergyGuide label for exact figures. SEER is a seasonal average — EER is closer to real draw on a hot day.
Is it cheaper to leave the AC on all day?
With inverter units, maintaining a moderate setpoint is often cheaper than repeated full-power cool-downs. With single-speed units, turning it off when away usually saves more.
How can I cut AC costs?
Raise the setpoint a couple of degrees and use fans, clean filters monthly, shade windows, and keep the outdoor unit ventilated. Each degree higher saves roughly 3–7%.
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