How it works
How to calculate it
The calculator applies the values you enter to this formula:
Cost = heater watts ÷ 1,000 × hours per day × days × rate.
How to use this calculator
- Read wattage for the selected heat setting.
- Estimate active heater hours.
- Enter days used and the marginal electricity rate.
Worked example
A 1,500 W heater used six hours daily consumes 270 kWh in 30 days.
Important assumptions
- The heater draws the entered power while active.
- Thermostat cycling can reduce consumption.
- This is an energy-cost estimate, not a heating-load calculation.
Common mistakes to avoid
- Assuming every hour plugged in is full-power use.
- Comparing room heating with whole-home heating without defining the heated area.
- Using the estimate as a safety or load assessment.
Method reviewed June 10, 2026. Prices and rates are user-provided defaults and should be replaced with local values.