Electric Space Heater Cost Calculator
Find out what your space heater costs to run, and what the same heat would cost from a gas furnace or a heat pump.
Sample numbers only, to show how it works. Replace them with yours.
Enter the watts of the heater (it is on the label or the box, often 1,500).
This is an estimate, not a professional calculation. See the disclaimer and the methodology.
How it is calculated
Energy = watts ÷ 1,000 × hours a day × days. Cost = energy × price per kWh. The cost per hour is the kilowatts times the price, and the cost per 30 days is the cost per day times 30.
Essentially all the electricity a resistance heater uses ends up as heat in the room, so the heat it gives is the kWh times 3,412 Btu (the EIA factor for one kWh). That lets us price the same heat from other sources.
The gas furnace line divides that heat by the AFUE of the furnace and by 100,000 Btu per therm, then multiplies by the gas price. The heat pump line divides the heat by its HSPF2, in Btu per watt-hour, and multiplies by the electricity price. The AFUE and HSPF2 start at the ENERGY STAR minimums (95 and 7.8) for certified equipment. Replace them with your own.
The prices start at the 2024 annual averages EIA reports for your state, so gas and electricity come from the same year. Replace them with the rates on your bills.
The hours are hours at full power. A heater with a thermostat switches off when the room is warm, so it draws power only part of the time. If you are not sure, measure with a plug-in watt meter for a day.
A space heater warms the room it is in. A furnace or a heat pump warms the whole home, so the comparison shows the cost of the same amount of heat, not what you would pay to heat the same space.
Worked examples
A 1,500 W heater for a winter
A 1,500 W heater running 8 hours a day for 90 days (assumed) uses 1,080 kWh. At the U.S. average of 16.5 cents per kWh (2024) it costs $0.25 an hour, $1.98 a day, $59 per 30 days and $178 for the 90 days.
The same heat from other sources
Those 1,080 kWh give 3.7 million Btu. A gas furnace at 95 AFUE and $1.40 per therm would make it for $54. A heat pump at HSPF2 7.8 would make it for $78. The space heater costs $178.
Power and hours move the bill
Halve the power to 750 W and the 90 days cost $89. Keep 1,500 W but run it 3 hours a day and they cost $67. Hours of use change the cost as much as the heater does.
Frequently asked questions
How much does it cost to run a space heater?
The cost per hour is the watts divided by 1,000 times your price per kWh. The calculator also gives the day, the month and the season for the hours you enter.
Is a space heater cheaper than central heat?
It can be if you heat one room and turn the rest down, but electric resistance heat costs more per unit of heat than a gas furnace or a heat pump in many states. The calculator compares the cost of the same heat three ways for your prices.
Does a thermostat on the heater lower the cost?
The heater draws power only while it is heating, so a thermostat turns it off when the room is warm. Enter the hours it actually runs, not the hours it is plugged in.
How many watts is a typical space heater?
The wattage is on the label or the box, and models differ. Enter the number from your heater. If it lists amps and volts, multiply them.
Why do the gas and heat pump lines use different units?
They are priced from the same amount of heat. The gas line uses AFUE and therms and the heat pump line uses HSPF2 and kWh. The calculator converts the heat so the dollars are comparable.
Related calculators
Sources and last update
- U.S. Energy Information Administration, 2024 Average Monthly Bill, Residential (average price by state)
- U.S. Energy Information Administration, Natural Gas Prices: Average Residential Price (annual, 2024)
- U.S. Energy Information Administration, Btu conversion factors
- ENERGY STAR, Air Source Heat Pumps key product criteria (HSPF2)
- ENERGY STAR, Furnaces key product criteria (AFUE)
- U.S. Energy Information Administration, copyrights and reuse
Last updated: November 3, 2026. See methodology and sources.