AC Running Cost Calculator Guide: Watts, Duty Cycle, and Monthly Cost
Use AC watts, daily hours, duty cycle, days, and kWh rate to estimate air conditioner electricity cost.
Last reviewed: July 5, 2026. This calculator is for monthly AC electricity cost, not BTU sizing. The key input is watts while running, then duty cycle adjusts for compressor cycling.
Input guide
| Input | How to choose it |
|---|---|
| Running watts | Use the AC label, manual, product page, or measured wattage. |
| Hours per day | How long the unit is available to run, not necessarily compressor-on time. |
| Duty cycle | Estimated percent of that time the compressor is active. |
| kWh rate | Use your electricity bill for the closest estimate. |
Example
A 1,200 W AC available 8 hours daily for 30 days at a 60% duty cycle uses 172.8 kWh. At $0.17/kWh, that is about $29.38 before fixed bill charges.
Choosing duty cycle
- Use a lower duty cycle for mild weather or shaded rooms.
- Use a higher duty cycle for hot weather, poor insulation, or low thermostat settings.
- If unsure, test 50%, 70%, and 90% to see the possible range.
Common confusion
BTU measures cooling capacity. Watts and kWh estimate electricity cost. A high-BTU efficient unit can cost less than a lower-BTU inefficient unit in some conditions.
Related calculator
Open the AC Running Cost Calculator to test your own numbers after reading the guide.