Most pages on this topic give you one number and stop. That number is useless to a reader in Honolulu and misleading to one in Baton Rouge. So here's the formula, a state-by-state table, and the one assumption that moves the result more than any other.
The formula takes ten seconds
Cost per hour = watts / 1,000 x your price per kWh.
A standard plug-in space heater is rated at 1,500 watts on its high setting. That's 1.5 kilowatts, so every hour it runs it uses 1.5 kWh. Multiply by what your utility charges and you're done.
The national average residential price was 18.31 cents per kWh in July 2026, up from 17.45 cents a year earlier, according to the U.S. Energy Information Administration. At that rate a 1,500-watt heater costs 27.5 cents an hour. Run it 8 hours and you've spent about $2.20.
Small. Then it adds up.
Cost by state
We took the July 2026 residential price for nine states and ran the arithmetic for 1,500 watts. The 30-day column assumes 8 hours a day at full power, which is 360 kWh a month.
| State | Price (cents/kWh) | Per hour | Per 8-hour day | 30 days |
|---|---|---|---|---|
| Louisiana | 12.72 | $0.19 | $1.53 | $45.79 |
| Washington | 14.71 | $0.22 | $1.77 | $52.96 |
| Florida | 15.03 | $0.23 | $1.80 | $54.11 |
| Texas | 15.88 | $0.24 | $1.91 | $57.17 |
| US average | 18.31 | $0.27 | $2.20 | $65.92 |
| Ohio | 19.45 | $0.29 | $2.33 | $70.02 |
| New York | 29.90 | $0.45 | $3.59 | $107.64 |
| Massachusetts | 30.49 | $0.46 | $3.66 | $109.76 |
| California | 33.61 | $0.50 | $4.03 | $121.00 |
| Hawaii | 48.00 | $0.72 | $5.76 | $172.80 |
Source: EIA Electric Power Monthly, Table 5.6.A, July 2026 residential prices. Our arithmetic; prices change monthly, and your own bill may add fixed fees or tiered rates.
The spread is the story. Hawaii costs 3.8 times what Louisiana does for the identical heater. If you've ever wondered why a friend in another state shrugs at a bill that made you wince, this is why.
The setting that changes everything: the thermostat
The table assumes the heater draws full power every minute. It doesn't. A heater with a working thermostat cycles off once the room reaches your setting.
How much does that save? It depends on the room, the weather and how well the door closes. We can't give you a universal percentage, and we'd distrust anyone who does. What we can say is the direction: a small, closed bedroom reaches its setpoint and coasts, so the real bill lands well under the table. A drafty garage never gets there, so the heater pulls full power all night and the table is the right answer.
If you want a real figure, plug the heater into an inexpensive plug-in energy meter for one evening and read the kWh. Then multiply by your rate.
Low setting: cheaper per hour, not always cheaper per degree
Most heaters offer a 750-watt or 900-watt step. Half the watts means half the cost per hour. It also means half the heat.
Here's the part people skip. Heat is what you're buying, not hours. A 1,500-watt heater produces about 5,100 BTU an hour. Run it at 750 watts and you get about 2,560 BTU. To heat the same room to the same temperature you need the same total energy, so the low setting just stretches the job out. The kilowatt-hours come out roughly the same.
The low setting does pay off in one case: holding a room that's already warm. That's maintenance, not heating.
Heater versus the alternatives
Every resistance heater turns one kWh of electricity into one kWh of heat. The 1,500-watt model, the oil-filled radiator and the ceramic tower are the same on that measure. Don't pay extra for marketing about "energy saving" modes without checking the watts.
A heat pump is a different animal. It moves heat instead of making it, so it can deliver more than 1 kWh of heat per kWh of electricity. Take a seasonal efficiency of 3 as a round, illustrative number, not a measured model: the same 1.5 kWh of heat would cost 0.5 kWh of electricity, or about 9 cents an hour at the US average rate. Which is the whole reason a mini-split can repay its price in a cold climate and a plug-in heater can't.
Here's our opinion, and you're free to disagree: if you heat the same room more than a few hours every day all winter, a space heater is the expensive way to do it. It's the right tool for an hour in the bathroom or a cold home office on a Tuesday.
What to check before you plug it in
- Read the watts on the label, not the box. 1,500 is the usual ceiling for a standard outlet.
- Look up your own rate on your bill. Cents per kWh is printed there.
- Run the formula for the hours you'd actually use it.
- Skip extension cords. Plug straight into the wall.
Next in this series: when an efficient dehumidifier repays its higher price, and when it never will. We'll use the same method, with the source and date on every number.
Questions about how we work? See the About page for our sourcing approach.