Space Heater Cost Calculator: Hourly & Monthly
A 1,500 watt space heater is one of the most expensive things you can plug into a wall outlet. Enter your hours and rate below to see exactly what yours costs.
Space heater running cost
Estimated cost per month
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Estimates use your rate × energy used. Real bills add fixed fees and taxes, and appliances that cycle (fridges, AC) vary with weather and use.
The quick answer
Almost every plug-in space heater sold in the United States tops out at 1,500 watts, because that is the most a standard 15 amp household circuit can safely deliver for hours at a time. At full power the heater uses exactly 1.5 kWh every hour it runs. Multiply that by your electricity rate and you have the cost per hour.
Those numbers use the U.S. average residential rate of 18.34¢ per kWh from the Energy Information Administration for June 2026. Rates vary a lot by state, from about 13¢ in Nevada to over 50¢ in Hawaii, so pick your state in the calculator or type the rate from your bill.
Cost by heater size and hours
Heaters come in a few standard sizes. Small desk heaters run 250 to 500 W, most portable units switch between 750 W (low) and 1,500 W (high), and a few 240 V garage or workshop heaters go to 4,000 or 5,000 W. Here is what each costs at the national average rate.
| Heater | Per hour | 4 h / day, monthly | 8 h / day, monthly | 24 h / day, monthly |
|---|---|---|---|---|
| 400 W | 7¢ | $8.92 | $17.84 | $53.52 |
| 750 W | 14¢ | $16.73 | $33.45 | $100 |
| 1,000 W | 18¢ | $22.30 | $44.60 | $134 |
| 1,500 W | 28¢ | $33.45 | $66.90 | $201 |
| 4,000 W | 73¢ | $89.21 | $178 | $535 |
One thing the table hides: a heater with a working thermostat rarely runs at full power the whole time. Once the room reaches the set temperature, the element switches off and only comes back on as the room cools. In a small, well-insulated bedroom a 1,500 W heater might actually draw power 40% of the time, cutting the real cost to well under half of the full-power figure. In a drafty room with the door open, it may never switch off at all.
Space heater vs turning up the furnace
The question people really want answered is whether the space heater is saving or costing them money. The honest answer is that it depends on how you use it.
Electric resistance heat is the most expensive kind of heat per unit delivered. One kWh of electricity produces 3,412 BTU of heat, so at 18.34¢ per kWh you pay about $5.38 per 100,000 BTU. Natural gas at a typical $1.50 per therm (100,000 BTU) in a 95% efficient furnace delivers the same heat for about $1.58. A heat pump moves heat rather than making it, so it delivers two to three units of heat for every unit of electricity, landing somewhere in between.
That makes the strategy clear:
- Zone heating saves money. If you spend the evening in one room, turning the whole-house thermostat down 5 to 8 degrees and running a 1,500 W heater in that room usually costs less than heating every room you are not in. The U.S. Department of Energy estimates roughly 1% savings on the heating bill for every degree the thermostat is lowered over an 8-hour period.
- Whole-house space heating does not. Running three or four heaters to replace a gas furnace typically doubles or triples the heating cost, and can overload circuits.
- If you already have a heat pump, the space heater is almost never cheaper. Just raise the heat pump setpoint.
Ways to cut the cost
- Use the thermostat, not the switch. Set a target temperature so the heater cycles instead of running flat out.
- Heat the person, not the room. A 100 W heated blanket or a 60 W heated foot pad costs 4 to 8 cents an hour and often replaces a 1,500 W heater entirely for someone sitting at a desk or in bed.
- Close the door and seal drafts. Heating a closed 12 by 12 room is easy; heating an open floor plan with a 1,500 W heater is impossible, and it will simply run all night.
- Put it on a timer or smart plug. Heat the bedroom for 45 minutes before bed and switch it off, rather than running it for eight hours.
- Check your rate plan. On a time-of-use plan, running a heater during the 4 to 9 pm peak can cost double. Pre-heat a room before the peak window starts.
For a wider view of where the winter bill goes, see the most expensive appliances to run and the appliance wattage chart.
Frequently asked questions
How much does it cost to run a 1,500 watt space heater for an hour?
A 1,500 W heater on high uses 1.5 kWh per hour. At the U.S. average of 18.34¢ per kWh that is about 28 cents an hour. In a high-rate state like California (34.74¢) it is about 52 cents, and in Nevada (13.11¢) about 20 cents.
How much does a space heater cost per month?
Running a 1,500 W heater 8 hours a day, every day, uses about 365 kWh a month, which costs roughly $67 at the national average rate. Cut it to 4 hours a day and the cost halves to about $33. Running it around the clock would cost about $200 a month.
Is it cheaper to use a space heater or central heating?
It depends on what you are heating. A space heater is cheaper only if it lets you keep the rest of the house colder. Heating one room with a 1,500 W heater while turning the furnace down several degrees usually saves money. Heating the whole house with several space heaters costs far more than a gas furnace or a heat pump.
Do oil-filled radiator heaters use less electricity?
No. An oil-filled heater rated at 1,500 W draws the same 1,500 W as a fan heater. The oil stores heat so the element cycles off for stretches, which can lower the average draw in a well-insulated room, but the heat it delivers per kWh is identical. All electric resistance heaters are 100% efficient at turning electricity into heat.
Does the low setting save money?
Only if it keeps the room warm enough on its own. Low is typically 750 W, half the power and half the cost per hour. But if it runs twice as long to reach the same temperature, you have spent the same energy. The real savings come from a thermostat that switches the heater off once the room is warm.
Is a space heater safe to run all night?
Manufacturers and fire-safety agencies generally advise against it. If you do, use a heater with tip-over and overheat shutoff, keep it three feet from bedding and curtains, plug it directly into the wall (never a power strip), and use a low setting with the thermostat. A heated blanket at 100 W is a far cheaper and safer way to stay warm in bed.