How Many Watts Does a Window Air Conditioner Use?
Window AC units vary widely in power consumption based on BTU rating. Smaller 5,000 BTU units are more practical for off-grid use than larger 12,000+ BTU models.
Typical Power
900W
Power Range
500-1500W
Startup Surge
2000W
Daily Usage
7200Wh
(8 hrs/day typical)
Window Air Conditioner Runtime Calculator
Range: 500-1500W
Continuous Runtime
0.9 hours
Days at 8hrs/day
0.1 days
Daily Consumption
7200Wh
Usable Battery
960Wh
Recommended Equipment
* Calculations assume 85% inverter efficiency and 80% depth of discharge (LiFePO4).
Battery Runtime Examples
| Battery Size | Voltage | Runtime at 900W |
|---|---|---|
| 200Ah | 12V | 2.2 hours |
| 400Ah | 12V | 4.4 hours |
| 600Ah | 12V | 6.7 hours |
* Assumes 85% inverter efficiency and 80% depth of discharge for LiFePO4 batteries.
Window Air Conditioner Power Tips
- •A 5,000 BTU window AC uses only 450-500W - much more battery-friendly
- •The compressor cycles on/off, so average draw is lower than rated watts
- •Install a soft-start to reduce startup surge by 50-60%
- •Inverter-type window ACs are 30-40% more efficient than standard models
- •Shade the outdoor side of the unit to improve efficiency
Frequently Asked Questions
How many watts does a window AC use?
5,000 BTU units use 450-500W, 8,000 BTU use 700-800W, 12,000 BTU use 1,000-1,200W. Always check the yellow EnergyGuide label for actual consumption.
Can I run window AC on solar?
A small 5,000 BTU unit is feasible with 600W of panels and 400Ah of batteries. Larger units require impractical amounts of solar and battery capacity.
What size inverter for window AC?
You need 2-3x the running watts to handle startup. For an 800W unit, use at least a 2000W pure sine wave inverter.