How many watts does a window air conditioner use?
Every number here comes from a named source. Generator charts give a generous figure for sizing a generator or power station. Test data and manufacturer specs show what the appliance draws.
- Running
- 667 to 3,250 W
- Extra at startup
- 3,950 W
- Voltage
- 120 V
How long it runs on a battery
| Battery | Runtime |
|---|---|
| 1 kWh | 1.3 h |
| 2 kWh | 2.5 h |
| 3 kWh | 3.8 h |
| 5 kWh | 6.4 h |
Running nonstop at 667 W, with 85% of the battery usable after inverter losses.
What each source says
| Figure | Value | Source and basis |
|---|---|---|
| Running | 667 (625 to 709) W | ENERGY STAR certified room air conditioners datasetENERGY STAR 120 V room air conditioners around 10,000 Btu/h, cooling capacity divided by CEER. Median of 112 models; range is the 10th to 90th percentile. |
| Running | 3,250 W | EWEB, Generator Sizing ConsiderationsGenerator sizing chart, 12,000 Btu window AC. |
| Extra at startup | 3,950 W | EWEB, Generator Sizing ConsiderationsGenerator sizing chart, 12,000 Btu window AC. |
| Running | 1,200 W | Amana Product Help, Generator Usage with AppliancesManufacturer's rough generator guide, 10,000 Btu air conditioner. |
By size
| Size | Running |
|---|---|
| 5,000 Btu/h | 347 (up to 365) W |
| 6,000 Btu/h | 438 (397 to 438) W |
| 8,000 Btu/h | 533 (500 to 569) W |
| 10,000 Btu/h | 667 (625 to 709) W |
| 12,000 Btu/h | 800 (750 to 863) W |
| 15,000 Btu/h | 1,042 (938 to 1,042) W |
ENERGY STAR 120 V room air conditioners, cooling capacity divided by CEER. Each row is the median of the certified models in that group, with the 10th to 90th percentile in brackets.
Good to know
- The EWEB and Generac charts list 3,250 W for a 12,000 Btu unit. Current ENERGY STAR models of that size run at about 800 W.
- Every 120 V model in the ENERGY STAR dataset lists a variable-speed compressor.
Sources
- ENERGY STAR certified room air conditioners dataset
- EWEB, Generator Sizing Considerations
- Amana Product Help, Generator Usage with Appliances
ENERGY STAR data downloaded on 2026-10-25. We publish the median of the certified models and the range from the 10th to the 90th percentile.