An 8,000 BTU window air conditioner uses about 660 watts. Common sizes run from about 440 W (5,000 BTU) to 1,100-1,200 W (12,000 BTU), and the compressor needs roughly 1,500 watts for a moment to start.
- Running watts
- 660 WTypical; 440–1,200 W across models
- Starting watts
- 1,500 WCompressor start surge, roughly 1.5-2.5x running for under a second…
- Per day
- 3.2 kWh8 h of use, cycling
- Current
- 5.5 AAt 120 V while running
Figures checked against DOE, ENERGY STAR and manufacturer data on . Your model's label is the final word.
Watts by model and setting
Most window air conditioner models draw between 440 and 1,200 W while running; a typical one draws about 660 W. Assumes an 8,000 BTU unit at 660 W for 8 hours with the compressor running about 60% of the time on a warm day.
- Size: about 440 W for 5,000 BTU, 660 W for 8,000 BTU and 1,100 W for 12,000 BTU on current models
- Efficiency: EER/CEER is BTU per watt, so a higher CEER means fewer watts for the same cooling; ENERGY STAR models must beat federal minimums
- Inverter (variable-speed) compressors throttle down instead of cycling, cutting average use
- Outdoor temperature, sun exposure, thermostat setting (78°F suggested) and how well the unit is sealed in the window
Running a window air conditioner on a generator or power station
- Generator: at least 660 running watts and 2,160 starting watts (running plus the 1,500 W start surge, the cautious way to size it). Check both numbers on the spec sheet. A generator rated 2,200 W or more covers it with room to spare.
- Power station: continuous output of at least 660 W and a surge rating that covers about 1,500 W. Pure sine wave output is the safe choice for motors and electronics.
| Power station capacity | Estimated runtime |
|---|---|
| 500 Wh | 1.1 h |
| 1,000 Wh | 2.1 h |
| 2,000 Wh | 4.3 h |
| 3,000 Wh | 6.4 h |
Based on 396 W average draw (running watts × duty cycle) and 85% usable capacity.
- Size the generator for the start surge, not just running watts: an 8,000 BTU unit typically needs about 1,500 W available to start
- Inverter generators of 2,000-2,200 W can usually run a 5,000-8,000 BTU unit; 12,000 BTU units are better matched to about 3,000 W
- Portable power stations need a pure sine wave inverter with surge capacity above the AC's starting draw; expect only a few hours of runtime from 1-2 kWh
- Generators belong outdoors, away from windows, including the window the AC is in, to keep carbon monoxide out
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Questions people ask
What size generator do I need for a window air conditioner?
Roughly 2,000 W for a 5,000-8,000 BTU unit and about 3,000 W for a 12,000 BTU unit, leaving headroom for the compressor start surge and anything else plugged in.
What do EER and CEER mean?
EER is cooling output in BTU per hour divided by watts; CEER also counts standby and fan-only power. An 8,000 BTU unit with an EER of 12 draws about 660 W.
How many amps does a window AC draw?
Small and mid-size 115 V units draw roughly 4 to 10 amps; for example, about 6 A for an 8,000 BTU model and 10 A for a 12,000 BTU model.
Sources
- GE AEM08LX 8,000 BTU window AC specifications (660 W, CEER 12.0)
- LG LW5016 5,000 BTU window AC specifications (440 W, CEER 11.0)
- Frigidaire FHWW122WC 12,000 BTU window AC spec sheet (1,100 W)
- ENERGY STAR: Room air conditioners
- ENERGY STAR: Room air conditioner key product criteria (CEER)
- Honda Power Equipment Canada: Generators guide, appliance running and starting watts