Space heater cost calculator
Updated
Enter the heater’s watts, hours of use and your electricity rate to see what a space heater costs per hour, day, month and season, and how that compares with central heating.
Next steps
How the calculation works
The formula is the Department of Energy’s: watts × hours used ÷ 1,000 = kilowatt-hours (kWh), then kWh × your rate = cost. A space heater needs one adjustment, because the thermostat switches the element off once the room is warm. The “time at full power” field covers that: 60% means the element is on about 36 minutes of every hour the heater is running.
Example 1 (the default values). A 1,500 W heater on high, 8 hours a day, 30 days a month, at full power 60% of the time, at 18¢ per kWh. Energy per day: 1.5 kW × 0.60 × 8 h = 7.2 kWh. Cost per day: 7.2 × $0.18 = $1.30. Cost per month: about $38.88. Over a 4-month season it comes to about $156.
Example 2. A 750 W setting, 10 hours a day, 30 days, 80% of the time at full power, at 15¢: 0.75 kW × 0.80 × 10 h = 6 kWh a day, which is $0.90 a day and $27.00 a month.
The central heating comparison. Every watt a space heater uses ends up as heat, so one kWh of electricity gives one kWh of heat (3,412 Btu). To price the same heat from a gas furnace, the calculator converts your gas price: one therm is 100,000 Btu, or about 29.3 kWh of heat, divided by the furnace efficiency. At $1.45 per therm and 95% efficiency, heat costs about 5.2¢ per kWh, against 18¢ for the electric heater. A heat pump moves heat instead of making it, so its cost is your electricity rate divided by its seasonal efficiency (COP). The Department of Energy says a modern heat pump can cut electricity use for heating by up to 75% compared with electric resistance heat.
The default gas price comes from the EIA’s residential average, which was about $15 per thousand cubic feet in February 2026. At 1,036 Btu per cubic foot that is roughly $1.44 per therm. Summer prices read higher because fixed charges are spread over less gas.
Common mistakes
- Assuming full power all day. With a working thermostat, a heater in a well-closed room cycles. Without one, enter 100.
- Comparing a room heater with a whole-house system. A 1,500 W heater warms one room. Central heating warms the whole house. The comparison above only prices equal amounts of heat. Space heating pays off only when the rest of the house is allowed to stay cooler.
- Using the wrong rate. Your effective rate includes delivery charges and taxes. If you are on a time-of-use plan, use the rate for the hours the heater runs; see time-of-use rates and your smart home.
- Trusting the label on a plug-in. The label shows the maximum. Use the general device calculator for other appliances.
- Skipping safety to save money. The U.S. Fire Administration and ESFI advise plugging heaters directly into a wall outlet and keeping them at least 3 feet from anything that can burn. See why a smart plug is a poor match for a space heater.
Frequently asked questions
How much does it cost to run a 1,500-watt space heater?
At 18¢ per kWh, a 1,500 W heater costs about 27¢ for each hour at full power. With a thermostat cycling the element on 60% of the time, it averages about 16¢ per hour, roughly $1.30 for 8 hours.
Is a space heater cheaper than central heating?
Not for the same amount of heat. Electric resistance heat costs more than gas heat and more than heat from a heat pump. A space heater can still save money if you lower the thermostat for the rest of the house and only heat the room you use.
Does a lower wattage setting cost less?
Yes, per hour. A 750 W setting uses half the power of a 1,500 W setting, but it also delivers half the heat, and a small heater may run longer to reach the same temperature.
How do I find my electricity rate?
Divide the total of a recent bill, minus fixed monthly charges, by the kWh used. The result includes delivery charges and taxes, which the energy charge alone leaves out.
Sources
- U.S. Department of Energy, Energy Saver — Estimating appliance and home electronic energy use
- U.S. Energy Information Administration — Short-Term Energy Outlook: electricity
- U.S. Fire Administration — Heating fire safety
- Electrical Safety Foundation International — Space heater safety
- U.S. Department of Energy, Energy Saver — Electric resistance heating
- U.S. Department of Energy, Energy Saver — Heat pump systems
- U.S. Energy Information Administration — British thermal units (Btu) and energy conversions
- U.S. Energy Information Administration — U.S. residential natural gas price