How to calculate space heater cost
Electric space heaters turn almost all of the electricity they use into heat, so the math is simple: power, time and your rate — adjusted for how often the thermostat switches the heater on.
- Convert watts to kilowatts. A 1,500 W heater draws 1.5 kW at full power.
- Apply thermostat cycling. At 60%, its average draw is 0.90 kW.
- Multiply by hours and your rate. 6 hours a day at 17.5¢/kWh is about $0.95 a day.
Cost = Watts × Cycling × Hours ÷ 1,000 × Price per kWh
Space heater cost by wattage
Per-hour costs at full power; monthly and seasonal costs at 6 hours a day with the thermostat cycling 60% of the time, 17.5¢/kWh — the U.S. average residential rate (EIA, 2025). Season = 5 months.
| Heater | Per hour | Per month | Per season |
|---|---|---|---|
| Personal / desk heater · 400 W | $0.070 | $7.67 | $38.33 |
| Small heater (low setting) · 750 W | $0.13 | $14.37 | $71.86 |
| Infrared heater · 1,000 W | $0.18 | $19.16 | $95.81 |
| Ceramic heater · 1,500 W | $0.26 | $28.74 | $143.72 |
Tips to lower space heater costs
- Heat the room you're in and lower the central thermostat for the rest of the house.
- Use the heater's thermostat or Eco mode instead of running it on High nonstop.
- Close doors and block drafts so the heater cycles off sooner.
- Plug heaters directly into a wall outlet — never an extension cord or power strip.
Frequently asked questions
How much does a 1500 watt heater cost per hour?
A 1,500 W heater running at full power uses 1.5 kWh per hour. At 17.5¢/kWh that's about $0.26 an hour. With a thermostat cycling it on and off, the real hourly cost is lower.
How much does it cost to run a space heater all month?
Running a 1,500 W heater 6 hours a day with the thermostat cycling 60% of the time costs about $28.74 a month at 17.5¢/kWh — around $143.72 over a 5-month heating season.
Are oil-filled or ceramic heaters cheaper to run?
At the same wattage, every electric resistance heater turns electricity into heat equally efficiently. A 1,500 W oil-filled radiator and a 1,500 W ceramic heater cost the same per hour at full power. Differences come from how they hold and spread heat, which affects how often the thermostat cycles.
Is a space heater cheaper than central heating?
It can be, if you heat one room and turn the whole-house thermostat down. Heating several rooms with space heaters is usually more expensive than a heat pump or gas furnace.
What does thermostat cycling mean?
A heater with a thermostat switches off once the room reaches the set temperature and back on when it cools. The cycling percentage is the share of time it actually heats — lower in a well-insulated room, higher in a cold or drafty one.
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