How this calculator works
A heater’s wattage is its power draw. Divide by 1,000 to get kilowatts, multiply by the hours it runs, and you have kilowatt-hours — the unit on your bill. Multiply by your price per kWh for the cost. If the heater has a thermostat, the element switches off once the room reaches temperature, so enter the share of time it is actually heating.
Assumptions and tips
- Uses the rated wattage; fan-only and eco modes draw less.
- Running two 1,500 W heaters on one 15 A circuit can trip the breaker.
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| Heater power | 1,500 W |
| Share of time the heating element is on | 100 % |
| Hours used per day | 8 h |
| Days per month | 30 |
| Months of heating | 5 |
| Electricity rate | 0.182 $/kWh |
| Number of heaters | 1 |
| Result | Value |
|---|---|
| Cost per hour | $0.273 |
| Cost per month | $65.52 |
| Cost per day | $2.18 |
| Cost per heating season | $328 |
| Energy per month | 360 kWh |
| Heat output | 5,118 Btu/h |
Step by step:
- Power = 1,500 W ÷ 1,000 × 100% × 1 = 1.5 kW
- Per hour = 1.5 kW × $0.182 = $0.273
- Per month = $0.273 × 8 h × 30 days = $65.52
Space heater running cost at 18.2¢/kWh (8 h a day, 30 days)
Calculated with this tool at the 2026 U.S. average electricity price.
| Heater | Cost per hour | Cost per month |
|---|---|---|
| 400 W | $0.073 | $17.47 |
| 750 W | $0.137 | $32.76 |
| 1000 W | $0.182 | $43.68 |
| 1500 W | $0.273 | $65.52 |
| 1500 W, cycling 60% | $0.164 | $39.31 |
Common mistakes to avoid
- Assuming “eco” heaters make more heat per watt — all resistance heaters are equally efficient.
- Heating a room while the central heat still warms the whole house.
Frequently asked questions
How much does a 1,500 W space heater cost per hour?
About 27 cents at the 2026 U.S. average of 18.2¢/kWh (1.5 kWh × $0.182).
How much does it cost to run a space heater all month?
Eight hours a day on high for 30 days is 360 kWh — about $66 at 18.2¢/kWh.
Is a space heater cheaper than central heat?
Only if you heat one room and turn the central heat down. Heating a whole house with resistance heaters costs more than a heat pump or gas furnace.
Sources
- U.S. Department of Energy: Estimating appliance and home electronic energy use
- U.S. EIA Short-Term Energy Outlook: electricity prices
Built and reviewed by Anirban Kundu, Creator & Editor · M.Sc Physics, 20 years teaching science