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The short answer: a standard 1,500-watt space heater running continuously for 8 hours uses 12 kWh. At the US average residential rate of about 17.5 cents per kWh (US Energy Information Administration) that is $2.10 per night, or roughly $63 a month if you run it nightly. It ranges from $1.32 a night in low-rate states to $3.84 in California and $5.28 in Hawaii. The formula is watts ÷ 1,000 × hours × your rate per kWh.
Most heaters cycle rather than run flat out, so real-world cost typically lands 30 to 60 percent below those figures once the thermostat starts shutting the element off. We do not physically handle the heaters we rank — our picks come from aggregated owner reviews and expert consensus, described in how we rank, with models in best space heater.
What does it cost at my electricity rate?
Two variables set the number: the heater’s wattage and your all-in rate per kilowatt-hour. Use the rate on your bill, not the advertised supply rate — dividing your total charge by kWh used captures delivery and fees, and typically comes out 15 to 40 percent higher. These are 8-hour costs at full output.
| Rate per kWh | 750 W (6 kWh) | 1,000 W (8 kWh) | 1,500 W (12 kWh) | 1,500 W × 30 nights |
|---|---|---|---|---|
| 11¢ — WA, ID, ND | $0.66 | $0.88 | $1.32 | $39.60 |
| 14¢ — TX, TN, MO | $0.84 | $1.12 | $1.68 | $50.40 |
| 17.5¢ — US average | $1.05 | $1.40 | $2.10 | $63.00 |
| 25¢ — NY, NH, VT | $1.50 | $2.00 | $3.00 | $90.00 |
| 32¢ — CA, MA, CT | $1.92 | $2.56 | $3.84 | $115.20 |
| 44¢ — HI | $2.64 | $3.52 | $5.28 | $158.40 |
How does that compare to other ways of heating the same room?
Resistance heating is the most expensive form of heat sold in the US per unit delivered, because it can only ever turn one unit of electricity into one unit of heat. A heat pump moves heat instead of making it, so it delivers two and a half to three and a half units for the same electricity. Gas delivers a cheaper unit to begin with. All figures below are for the same 41,000 BTU of heat, which is what 12 kWh of resistance heat produces.
| Heat source | Efficiency | Cost for the same heat |
|---|---|---|
| Electric space heater, 1,500 W | 100% | $2.10 |
| Ductless heat pump, COP 3.0 | 300% | $0.70 |
| Natural gas furnace, 95% AFUE | 95% | $0.65 – $0.90 |
| Propane furnace, 95% AFUE | 95% | $1.40 – $1.90 |
| Heat pump at 5°F, COP 1.8 | 180% | $1.17 |
The case for a space heater is not efficiency, it is targeting. Heating one occupied 150 square foot room while dropping the whole-house thermostat 6 to 8°F is a real saving in a large or poorly zoned home. Running several at once alongside a furnace is how people end up with a $400 January bill.
How many amps does a 1,500-watt heater draw?
Amps equal watts divided by volts: 1,500 ÷ 120 = 12.5 amps. That single number explains every warning printed on the box. The National Electrical Code treats a load running three hours or more as continuous and limits it to 80 percent of the circuit rating, which is 12 amps on a 15-amp circuit and 16 amps on a 20-amp circuit. A 1,500-watt heater is therefore already at or slightly over the continuous limit of a standard 15-amp bedroom circuit before anything else is plugged in.
- Plug directly into a wall receptacle. Manufacturers, the CPSC and the NFPA all say the same thing: no extension cords, no power strips, no surge protectors. Those cords are typically rated for far less than 12.5 amps continuous and the connection heats up.
- Never daisy-chain a heater behind another strip or a timer, and never run two heaters on one circuit — 25 amps on a 15-amp breaker is not a nuisance trip, it is what happens before one.
- Give it its own circuit where possible, and if there is no suitable outlet, have a licensed electrician add one. Do not modify wiring, replace a breaker with a larger one, or change an outlet yourself.
- Heat at the plug is a warning. A receptacle or plug that is warm to the touch, discolored or smells of hot plastic means a loose connection — unplug it and stop using that outlet.
- Three feet of clearance in all directions from bedding, curtains, furniture and paper, on a hard level surface.
If a room needs a heater every night all winter, the running cost usually justifies fixing the cause instead. Weigh it against a permanent solution in how much does it cost to install a mini split, and check the heating side of your existing system in why does my furnace short cycle. If the goal is holding a whole house at a lower setpoint safely, how low can you set a thermostat before pipes freeze has the floor you should not go under.