How to work out what a space heater costs
Electricity is billed in kilowatt-hours (kWh): 1,000 watts running for one hour. A space heater's wattage is on its label, so the math takes four steps. Here it is with the values the calculator opens with: a 1,500-watt heater on high, 4 hours a day, 30 days a month, a 5-month winter and the U.S. average rate.
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1
Turn watts into kilowatts
Divide by 1,000. A 1,500 W heater draws 1.5 kW, so it uses 1.5 kWh for every hour it runs.
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2
Multiply by your rate for the cost per hour
1.5 kWh × $0.1816 (the U.S. average in August 2026, per the EIA) = $0.27 an hour.
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3
Multiply by hours and days
4 hours a day is 6 kWh, or $1.09. Over 30 days that is 180 kWh and $32.69 a month.
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4
Multiply by the months you heat
5 months (November to March) comes to 900 kWh and $163 for the winter.
Two things push the real number around. First, heaters with a thermostat cycle off once the room is warm, so a heater "on" for 8 hours may only heat for 4 or 5. Second, your utility's rate is rarely the state average. The calculator lets you fix both: set the hours to heating time and type in your own rate.
What each setting costs
Almost every plug-in heater sold in the U.S. tops out at 1,500 watts, the most a standard 15-amp, 120-volt outlet can safely carry for hours on end. Low settings are usually 600 to 900 watts. Small personal heaters can be 200 to 500 watts. Each watt makes about 3.41 BTU of heat an hour.
| Watts | BTU/hour | Per hour | Per month* |
|---|---|---|---|
| 400 (personal) | 1,365 | 7¢ | $8.72 |
| 750 (low) | 2,559 | 14¢ | $16.34 |
| 900 (low) | 3,071 | 16¢ | $19.61 |
| 1,000 | 3,412 | 18¢ | $21.79 |
| 1,500 (high) | 5,118 | 27¢ | $32.69 |
*4 hours a day for 30 days at the August 2026 U.S. average of 18.16¢ per kWh.
Cost to run a 1,500 W heater by state
The same heater costs almost four times as much in Hawaii as in Nevada. Average residential prices for August 2026 from the EIA, the same rates the calculator loads. Tap a state to load it.
| State | Per hour | Per month* | Winter* |
|---|---|---|---|
| Hawaii | 71¢ | $84.92 | $425 |
| Maine | 48¢ | $57.80 | $289 |
| Massachusetts | 46¢ | $54.86 | $274 |
| California | 45¢ | $53.55 | $268 |
| New York | 43¢ | $51.57 | $258 |
| Michigan | 34¢ | $41.38 | $207 |
| Pennsylvania | 33¢ | $39.19 | $196 |
| Ohio | 29¢ | $34.88 | $174 |
| Illinois | 29¢ | $34.78 | $174 |
| U.S. average | 27¢ | $32.69 | $163 |
| Texas | 24¢ | $28.64 | $143 |
| Georgia | 24¢ | $28.62 | $143 |
| Florida | 22¢ | $26.98 | $135 |
| Washington | 22¢ | $26.33 | $132 |
| Tennessee | 20¢ | $24.16 | $121 |
| Louisiana | 19¢ | $23.17 | $116 |
| Nevada | 19¢ | $22.90 | $114 |
*1,500 W, 4 hours a day, 30 days a month; winter is 5 months. All 50 states and D.C. are in the calculator's list.
Does a space heater save money?
Honestly, it depends on what it replaces. Every plug-in electric heater turns about 100% of its electricity into heat, which sounds efficient. But electricity is an expensive way to buy heat. A heat pump moves heat in from outdoors and, per the DOE, can cut the electricity used for heating by about half compared with resistance heat. A gas furnace burns fuel that costs far less per BTU. The comparison box above prices the heat your heater makes each month from all three.
With the default numbers, the heater's 180 kWh a month makes about 614,000 BTU of heat. A heat pump would make it for about $16 and a 90% gas furnace for about $10, at the U.S. winter gas price of $1.43 per therm. The space heater costs $33.
So where does a space heater win? When it lets you heat one room instead of the whole house. If you work from a home office all day, setting the central thermostat back several degrees and warming just that room can cost less overall. The DOE's guidance is the same: use a space heater to supplement the main system in a room you're in, not to replace it. If you run heaters in three rooms while the furnace runs too, you pay twice.
- Good use: one cold room, a few hours a day, with the main thermostat turned down.
- Costly use: heating a drafty room all day because the main system can't keep up. Fix the draft or the system instead.
- Worst use: as the only heat for a whole house through the winter. At 24 hours a day, one heater costs about $196 a month at the national average.
Which type of heater to buy
Since every 1,500 W heater makes the same heat, the type changes comfort, not cost per hour. A heater with a good thermostat costs less because it runs fewer hours.
| Type | Best for |
|---|---|
| Ceramic fan | Quick heat in a small room or bathroom; makes some fan noise |
| Oil-filled radiator | Quiet, steady heat in a bedroom; slow to warm up, stays warm after it cycles off |
| Infrared (radiant) | Warming a person at a desk or chair in a large or drafty space |
| Electric blanket or heated pad | Staying warm in bed or on the couch for 50 to 200 watts |
A common rule of thumb is 10 watts per square foot of room, so 1,500 W suits about 150 square feet with standard ceilings. For a bigger or colder room, a plug-in heater will run nonstop and still fall short.
Space heater safety
Space heaters are a leading cause of home heating fires. In the National Fire Protection Association's 2011–2015 analysis, they were involved in about two of every five home heating fires and five of every six deaths from them. The Consumer Product Safety Commission estimates that portable heaters were involved in about 1,700 fires and 70 deaths a year from 2017 to 2019. Most of these fires start when something that can burn is too close. The rules from the NFPA and the Consumer Product Safety Commission are simple:
- 3 feet of clearance on all sides from bedding, curtains, furniture, clothes and paper.
- Wall outlet only. A 1,500 W heater draws about 12.5 amps. Light-duty extension cords and power strips can overheat at that load. If the plug or outlet gets hot, stop using it and have an electrician check the outlet.
- Hard, level floor, out of walkways and away from kids and pets.
- Automatic shut-off for tip-over and overheating, and a certification mark from a testing lab.
- Off when you leave or sleep. Keep working smoke alarms on every level.
Fuel-burning heaters (kerosene or propane) add carbon monoxide risk and are not covered by this calculator. If a room needs a heater every day, a licensed electrician can add a dedicated circuit or a hard-wired wall heater, which is safer than a plug-in unit working at its limit.
Common questions
How much does it cost to run a space heater per hour?
A 1,500-watt space heater on high uses 1.5 kWh every hour. At the August 2026 U.S. average of 18.16 cents per kWh, that is about 27 cents an hour. On a 750-watt low setting it is about 14 cents. In Hawaii it is about 71 cents an hour on high, and in Nevada about 19 cents.
How much does it cost to run a space heater 24 hours a day?
A 1,500-watt heater running nonstop uses 36 kWh a day. At 18.16 cents per kWh that is about $6.54 a day, or $196 over 30 days. A thermostat that cycles the heater off cuts this, but heaters left on all day are often the reason a winter bill jumps.
Is it cheaper to use a space heater or central heat?
Per unit of heat, a space heater is usually the most expensive option: a gas furnace or a heat pump makes the same heat for less. A space heater saves money only when it lets you turn the central thermostat down and heat one room instead of the whole house.
Are oil-filled, ceramic or infrared heaters more efficient?
No. Every plug-in electric heater turns about 100% of its electricity into heat, so 1,500 watts makes the same amount of heat whatever the type. They differ in how they deliver it: infrared warms you directly, ceramic fans heat the air quickly, and oil-filled radiators heat slowly and stay warm.
Can I plug a space heater into an extension cord or power strip?
No. Safety agencies say to plug a space heater directly into a wall outlet. A 1,500-watt heater draws about 12.5 amps, which can overheat a light-duty extension cord or power strip and start a fire. Avoid sharing that outlet with other large loads too.
How big a room can a 1,500-watt space heater heat?
A common rule of thumb is 10 watts per square foot, so a 1,500-watt heater suits a room of about 150 square feet with 8-foot ceilings and average insulation. Drafty rooms, high ceilings and cold climates need more, which a single plug-in heater cannot provide.
Sources and assumptions
- Electricity rates: U.S. Energy Information Administration, Electric Power Monthly, Table 5.6.A, average residential price for August 2026 (preliminary). These are the same rates as our electric bill calculator.
- Natural gas price: EIA, U.S. price of natural gas delivered to residential consumers, average of November 2025 to March 2026 ($14.85 per thousand cubic feet), converted at 1,038 BTU per cubic foot to $1.43 per therm. Summer prices run higher because fixed charges are spread over less gas.
- Comparison: 1 kWh = 3,412 BTU. Electric resistance heat counted at 100% efficient; heat pump at 2 units of heat per unit of electricity, in line with the DOE's statement that heat pumps cut heating electricity by about half (DOE Energy Saver, Heat Pump Systems); gas furnace at 90% efficiency. Newer cold-climate heat pumps and 95% furnaces do better. The comparison prices the same amount of heat, not the cost of heating a whole house.
- Using heaters: DOE Energy Saver, Portable Heaters.
- Safety: NFPA heating safety and its Home Fires Involving Heating Equipment report (2011–2015 data); CPSC winter heating warning (January 2023), source of the 1,700 fires a year figure.
- Sizing: 10 watts per square foot is a rule of thumb used by heater makers, not a standard. The calculator ignores fixed monthly fees, tiered or time-of-use rates and taxes unless you fold them into your own rate.