How much a space heater costs to run
Nearly every plug-in space heater — ceramic, oil-filled radiator or infrared — turns electricity into heat at the same rate: 1 watt makes 3.412 Btu per hour, regardless of style. So the cost comes down to the wattage setting, the hours it runs, how much of each hour the thermostat keeps the element on, and your price per kWh.
Worked example: a 1,500 W heater on high is 1.5 kW. Running 8 hours uses 12 kWh. At the U.S. average residential price of 18.19¢/kWh (Jan–Aug 2026, EIA) that's $2.18 a day and $66.40 over a 30-day month.
| Setting | Per hour | 8 h a day, per month | 24 h a day, per month |
|---|---|---|---|
| 1,500 W | $0.27 | $66.40 | $199.20 |
| 900 W | $0.16 | $39.84 | $119.52 |
| 750 W | $0.14 | $33.20 | $99.60 |
Those are full-power figures at the U.S. average price. Where you live changes them a lot:
| State | ¢/kWh (Jan–Aug 2026) | 1,500 W, per hour | 8 h a day, per month |
|---|---|---|---|
| Hawaii | 46.41 | $0.70 | $169.42 |
| California | 32.58 | $0.49 | $118.93 |
| Maine | 30.23 | $0.45 | $110.35 |
| Idaho | 13.02 | $0.20 | $47.53 |
| Nebraska | 12.92 | $0.19 | $47.16 |
| North Dakota | 12.46 | $0.19 | $45.48 |
Thermostats: why real bills are lower than the maximum
A heater with a thermostat switches its element off once the room reaches the set temperature and back on as it cools. In a closed, reasonably insulated room it may run only 40–70% of each hour; in a drafty room on a cold night it can run nonstop. The calculator shows the full-power figure and the thermostat range side by side. The low setting (often 900 or 750 W) uses less per hour but also delivers less heat, so it only saves money if the room still stays warm enough.
Space heater or central heat?
Compare the cost of the heat itself. At U.S. average prices, resistance heat costs $53.31 per million Btu, against $15.59 from a 95%-efficient gas furnace at $1.48/therm and about $21.55 from an average ENERGY STAR heat pump (HSPF2 8.44). Per unit of heat, a space heater is the most expensive way to warm a house that has gas or a heat pump. It wins only when it lets you turn the whole-house thermostat down several degrees while you heat the one room you're using. In a home with electric baseboards or furnace heat strips, a space heater costs the same per Btu — the saving comes from heating fewer rooms, not from the heater.
Each state page above works out that comparison with local electricity, natural gas, propane and heating-oil prices, and counts how many months average below 60°F there using NOAA climate normals.
Safety rules that also save money
- A 1,500 W heater draws 12.5 A at 120 V. Plug it straight into a wall outlet — never an extension cord or power strip.
- Two 1,500 W heaters on one 15 A household circuit will trip the breaker or overheat the wiring.
- Keep 3 feet of clearance and choose a model with tip-over and overheat shut-off.
- Don't shut the central heat off completely in freezing weather: pipes in outside walls can freeze.
- Never heat a room with a gas oven or range.
Common mistakes when estimating
- Assuming the low setting is "efficient." Every resistance heater is 100% efficient; low just makes less heat.
- Using an old national rate. Many articles still use the 16–17¢/kWh averages of 2024–2025; the U.S. average for Jan–Aug 2026 is 18.19¢.
- Ignoring the season. A month of nightly use in a cold state is the norm; in Florida a heater may run only on a handful of cold nights.
Comparing whole-house options? See what the electricity for heat pump cooling costs, check your state's electricity rate, or price any other appliance with the electricity cost calculator.