AC Running Cost Guide: How Much Does an Air Conditioner Cost to Run?
Understand how AC running cost changes with wattage, duty cycle, thermostat setting, insulation, climate, and daily usage.
Last reviewed: July 5, 2026. Air conditioners do not usually pull their full running wattage every minute of the day. This guide explains duty cycle and why it matters.
The cost formula
Formula: running watts ÷ 1,000 × hours × days × duty cycle × electricity rate.
Duty cycle is the estimated percentage of time the compressor is actually running. A unit set to a moderate temperature in a shaded room may cycle less. A unit in a sunny, poorly insulated room may run much longer.
Example with duty cycle
| Situation | Input | Estimated monthly cost |
|---|---|---|
| Moderate use | 1,200 W × 8 h × 30 days × 50% × $0.17 | 86.4 kWh · $14.69 |
| Heavy summer use | 1,200 W × 12 h × 30 days × 80% × $0.17 | 345.6 kWh · $58.75 |
What increases AC cost
- Low thermostat setting during hot weather.
- Direct afternoon sun on windows and walls.
- Poor insulation or air leaks around doors and windows.
- Oversized rooms, open doors, or connected spaces.
- Dirty filters or blocked airflow.
Ways to make the estimate more realistic
- Use the wattage from the unit label when possible.
- Estimate separate summer and shoulder-season usage.
- Track one week of use and multiply carefully instead of guessing a whole month.
- Compare the calculator result with your actual bill after the first month.
Related calculator
Use the AC Running Cost Calculator to test your own numbers after reading the guide.