HVAC calculator
AC Running Cost Calculator
Estimate the electricity used by an air conditioner based on power input, hours of use, and an adjustable operating assumption.
AC operating assumptions
Watts (W). Use measured average input if available.
Percent of switched-on hours
100% means the unit draws the entered wattage for all hours. A lower percentage is an illustrative adjustment for cycling or variable-speed operation; it is not a measured efficiency rating.
USD per kWh
Estimated AC energy cost
Monthly electricity cost
$32.26
Monthly energy use
201.6 kWh
Annual cost (same monthly use × 12)
$387.07
Monthly cost at 100% entered power
$46.08
Formula: watts ÷ 1,000 × hours/day × days/month × equivalent full-power percentage × USD/kWh.
How this tool works
Enter electrical input in watts, not cooling capacity in BTU/h. The calculation converts watts to kilowatts and multiplies by hours, days, and your electricity rate.
For cycling or variable-speed units, an equivalent full-power runtime percentage can approximate reduced average input. For example, 70% means the tool treats eight switched-on hours as 5.6 hours at the entered wattage.
Limitations and next steps
Actual AC use depends on outdoor temperature, thermostat setting, insulation, system sizing, humidity, and equipment behavior. Variable-speed units do not necessarily use a constant wattage when running.
For a more reliable estimate, use measured kWh or manufacturer seasonal energy information. The annual figure assumes identical use for all 12 months and may overstate costs in seasonal climates.