By the SavingsRoll Team | Personal Finance
A space heater turns every watt it pulls from the wall into heat. That makes it 100% efficient, and it can still raise your winter bill, because efficiency isn’t what you pay for. You pay for each unit of heat, and if your furnace runs on natural gas, a plug-in heater buys the same warmth at roughly 3.8 times the price. So do space heaters save money? Before you plug one in under your desk this month, run the numbers below. It takes about three minutes, and for a lot of people the answer turns out to be a heated throw, not a heater.
Electric heat costs nearly four times what gas heat costs
Start with the prices, because they decide everything. The national average residential electricity price was 18.31 cents per kilowatt-hour in July 2026, up 4.9% from a year earlier, according to the U.S. Energy Information Administration. Natural gas delivered to homes averaged $13.96 per thousand cubic feet in January 2026, per EIA’s residential natural gas price series.
Those units don’t line up, so convert them both to a therm, which is 100,000 BTUs of heat. A thousand cubic feet of gas holds about 10.36 therms, which puts gas at roughly $1.35 per therm. A modern 95% efficient furnace turns that into about $1.42 per therm of heat that actually reaches your rooms. A therm of electric heat takes 29.3 kWh, and at 18.31 cents that comes to $5.37.
So $5.37 against $1.42. Every bit of warmth a space heater adds to a gas-heated house costs 3.8 times what the furnace would have charged for the same warmth. Heat pump owners face a similar gap. The Department of Energy says a heat pump can cut the electricity used for heating by up to 75% compared with resistance heaters, so in a heat pump home a plug-in unit can cost up to four times as much per unit of heat.
Do space heaters save money? Only when the thermostat goes down
Every guide on this topic says the same thing: a space heater saves money if you heat only the room you’re in. That’s half true. It saves money only if you also turn the whole-house thermostat down far enough to save more on gas than you spend on electricity, and at a 3.8 to 1 price ratio that’s a much bigger cut than people expect.
The DOE’s rule of thumb is that setting the thermostat back 7 to 10 degrees for 8 hours a day saves as much as 10% a year on heating, or roughly 1% per degree for each 8-hour stretch. On a $200 gas bill, a 10 degree setback during workdays is worth about $14.67 a month (the math is below). A 1,500-watt heater running flat out at 27 cents an hour burns through that in about 53 hours, which is less than seven workdays. And if the heater runs while the furnace still holds the rest of the house at 70, you aren’t saving anything at all. You’re paying for both.
The home-office space heater usually loses money
The setup I see most often: someone works from home, the office runs cold, and a 1,500-watt heater goes under the desk. Say your January gas bill is $200 and you work 22 days a month.
A 1,500-watt heater on its own thermostat usually cycles on and off. Call it an average of 750 watts over an 8-hour workday. That’s 6 kWh a day, or 132 kWh over 22 days, which at 18.31 cents comes to $24.17 for the month.
That’s the space heater cost to run. Now credit the thermostat setback savings. Drop the house from 70 to 60 during work hours and the DOE rule gives you about 10% on those days. Twenty-two of thirty days is 73% of the month, so you save about 7.3% of $200, or $14.67. Subtract the heater and you’re down $9.50 for the month. You got colder hallways and a bigger total bill.
Push the heater to high all day and it gets worse: 1.5 kWh an hour is 27 cents an hour, or about $48 over the same 176 work hours.
Heating yourself costs a fraction of heating the room
What fixes the math is shrinking the thing you heat from a room to a person. A heated throw or mattress pad in the 100-watt range (check the label, since many draw less) uses 0.8 kWh over eight hours. That’s under 15 cents a day.
Run the same office scenario with a heated throw instead of the heater: 17.6 kWh over 22 workdays, or $3.22. The setback still saves $14.67, so you come out $11.45 ahead instead of $9.50 behind. That’s a $20.95 swing a month, and the only thing you changed was what you plugged in.
Do the same thing at night. Set the house back 10 degrees for 8 hours every night and the DOE rule puts the savings near 10% of the bill, or $20. A heated mattress pad running those same 8 hours costs about $4.39 a month. Net, you’re $15.61 ahead. Add the daytime and nighttime moves together and a household with a $200 January gas bill keeps about $27 a month. Over a five-month heating season, that’s roughly $135, from two small plug-in purchases you make once.
The blanket also wins on a number that has nothing to do with your bill. The National Fire Protection Association counted an average of 38,881 home heating equipment fires a year from 2019 to 2023. Space heaters and heating stoves were involved in 29% of those fires but 77% of the deaths. If you do use one, keep it three feet from anything that burns, plug it straight into the wall, and turn it off when you leave the room.
Your bill tells you which house you live in
The space heater advice you read online assumes everyone heats with the same fuel. They don’t. Pull up last January’s bills and find two things: what fuel your main heat uses, and what you pay per therm or kWh on the delivery and supply lines combined.
If you heat with gas or have a heat pump, the plug-in heater is the expensive tool. Use it in short bursts in a small room with the thermostat set back hard, or skip it and heat yourself. If your house has electric baseboard or a resistance furnace, the heater and your main heat cost the same per unit, so the savings come entirely from turning down the baseboards in rooms you aren’t using. Oil and propane homes sit closer to the middle, so plug your own per-gallon price into the same math before you decide.
If the setback is where the money is, make it automatic. A programmable thermostat that drops to 60 at 9 a.m. and 10 p.m. will do it every day without you thinking about it. We covered the bigger winter moves, sealing air leaks and shopping your electricity rate, in our guides to weatherizing before the cold and switching electricity plans before winter. This one takes a single bill and a few minutes with a calculator. Do space heaters save money? In a gas-heated house, mostly no, but the setback they’re supposed to make possible does, and you can get it for a fraction of the cost.
