The short answer
In Northern Virginia, a space heater saves money when you heat one room for a few hours and turn the whole house down. It costs more when you use it to stand in for a furnace or heat pump. A plug-in heater pulls 1,500 watts on high, which is about $1.80 for an eight-hour night at Dominion’s roughly 15 cents a kilowatt hour, $5.40 if it runs all day, and about $162 over 30 days of that. And if you’re reaching for it because one room never warms up, the heater is covering for something worth fixing.
The math, one heater at a time
Every plug-in space heater tops out at 1,500 watts, because that’s what a regular household outlet can safely carry. That’s 1.5 kilowatt hours for every hour it runs on high. Dominion’s residential customers pay roughly 14.7 to 15 cents per kilowatt hour once you add up the charges on the bill, so use 15 cents and check your own bill for the real figure.
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| How you run it | Electricity | About what it costs |
|---|---|---|
| One evening, 4 hours | 6 kWh | $0.90 |
| One night, 8 hours | 12 kWh | $1.80 |
| All day, 24 hours | 36 kWh | $5.40 |
| All day for 30 days | 1,080 kWh | $162 |
| Two heaters, all day for 30 days | 2,160 kWh | $324 |
Those 1,500 watts put out about 5,100 BTUs an hour. A furnace in a typical Northern Virginia house is sized somewhere around 60,000 to 100,000 BTUs. So one space heater is a small fraction of what it takes to heat a house, and that’s why it works for one room and fails as a whole-house plan.
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When the space heater wins
- You’re in one room for the evening. Set the thermostat down 4 to 6 degrees and heat the room you’re sitting in. The house loses less heat to the outside when it’s cooler inside, and that’s where the savings come from.
- A home office. Heating one 120 square foot room for an eight-hour workday while the rest of the house sits at 62 usually beats heating all of it to 70.
- A short cold snap in a mild room. A few days, a few hours each, is cheap.
When the furnace or heat pump wins
- You have a heat pump. In ordinary Northern Virginia winter weather, a heat pump moves two to three units of heat into the house for each unit of electricity it uses. A space heater makes exactly one. Same electric bill, a fraction of the heat. Our post on heat pump vs gas furnace costs runs those numbers for a whole house.
- You’re running two or three heaters. At that point you’re paying electric resistance rates to heat most of the house, and gas heat or a heat pump does that for less.
- You leave the thermostat where it was. If the furnace still runs at 70 and you add a space heater on top, you’re paying for both.
When the space heater is telling you something
Most of the calls we get that start with “we’ve been using a space heater” end with something we can fix. One room that never warms up is usually airflow: a crushed or disconnected duct, a closed damper, a return that can’t breathe. A house that never reaches the setting is a furnace or heat pump that isn’t putting out what it should, a dirty blower wheel or a heat pump that’s short on refrigerant. We wrote up the one cold room causes separately.
Our heating check is $67 per system, through December 31. On a furnace we can also pull the blower wheel and clean it blade by blade for $229 (regularly $467), which is often the fix for weak airflow. If your bill already jumped, read what a doubled heating bill usually means first.
Using one safely
- Plug it straight into a wall outlet. Never an extension cord or a power strip.
- Three feet of clear space all around: curtains, bedding, paper, the dog’s bed.
- Buy one with tip-over and overheat shutoff, and turn it off when you leave the room or go to sleep.
- Electric heaters don’t make carbon monoxide. Kerosene and propane heaters meant for outdoors do, and they don’t belong inside. If an alarm goes off, here’s what to do when the CO alarm goes off.
The full list is in space heater safety: what not to do. And if you’ve heard that closing vents in empty rooms saves money, that’s one of the six myths we bust.
Call us
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Questions people ask
Is it cheaper to run a space heater or the furnace?
For one room for a few hours with the thermostat turned down, the space heater. For the whole house, or with a heat pump, the furnace or heat pump. A 1,500 watt heater costs about $1.80 for an eight-hour night at 15 cents a kilowatt hour.
How much does it cost to run a space heater all day?
About $5.40 a day on high at 15 cents a kilowatt hour, which is roughly Dominion’s 2026 residential rate, and about $162 over 30 days.
Is a space heater cheaper than a heat pump?
Almost never. A heat pump moves two to three units of heat for each unit of electricity in normal winter weather, while a space heater makes one.
Why do I need a space heater in one room?
Usually airflow: a crushed or disconnected duct, a closed damper, a blocked return, or a dirty blower wheel. It’s worth a heating check before another winter of the heater.
