Calculate your cost
Start with the example below, then replace the wattage, daily runtime, and rate with the numbers for your central air conditioner.
This setup uses about 840 kWh in a 30-day month.
Please enter valid values within the ranges shown.
| Schedule | Hours/day | Cost/month |
|---|---|---|
| Half runtime | 4 | $79.09 |
| Page example | 8 | $158.17 |
| Longer runtime | 12 | $237.26 |
Same 3,500-watt input and 18.83¢/kWh rate; only runtime changes.
Formula for the page example
3.5 kW × 8 hr × $0.1883 = $5.27 per day
Convert watts to kilowatts, multiply by the active hours used each day, then multiply by the electricity price in dollars per kWh. Multiply the daily result by 30 for the monthly estimate shown above.
How to read this estimate
Central air conditioning can account for a large share of summer electricity use. Since the compressor cycles instead of drawing full power continuously, a measured average or realistic active runtime will give you a closer estimate than nameplate watts alone.
Use this as a baseline until you can check the label or measure the central air conditioner directly. Model, settings, condition, climate, and household routine can all change the result.
What changes the cost?
- 01
Cooling capacity and system efficiency rating
- 02
Outdoor temperature, humidity, and thermostat setting
- 03
Home size, insulation, duct leakage, and compressor runtime
Ways to spend less
- Raise the thermostat a few degrees when the home is empty.
- Replace dirty filters and keep outdoor coils clear.
- Seal duct leaks and shade sun-facing windows before oversizing equipment.