Short answer
A typical 1,500-watt space heater costs about $0.27 an hour at the 2026 U.S. average electricity rate, roughly $2.16 for an 8-hour night, or $65 for a full month of nightly use. A smaller 400–900W unit on a working thermostat costs a third to half of that. The setting matters more than the brand.
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This is the math behind what a space heater costs to run: what the wattage on the box means, how thermostat cycling changes the real number, and what to know about the plug-in energy savers people keep asking about. (For summer cooling, the cooling section of the pillar guide shows which kind of cooler fits which climate.)
How much electricity does a space heater actually use?
Almost every portable space heater sold in the U.S. falls between 400 and 1,500 watts, and most have a dial or button that switches between two or three of those levels. The 1,500W ceiling is not a marketing choice: it comes from the 15-amp household circuit, and the arithmetic is in the small-room heater guide.
Watts translate to cost through one fixed formula: kilowatts × hours run × your price per kilowatt-hour. A 1,500W heater is 1.5 kilowatts. Run it for one hour and it uses 1.5 kWh. That's the whole calculation: the only variable that changes by heater is the wattage, and the only variable that changes by location is your electricity rate.
One thing worth knowing before you plug in numbers: the figure printed on the box is the heater's rated power, which makes it a very good starting point for planning. The next section shows how to read your own unit in five minutes, so the number you use is the one from your own wall.
How do I check my own heater's real cost in 5 minutes?
A plug-in wattmeter (sold as a "Kill A Watt" or generic "power meter," usually $12–$20) sits between the heater and the outlet and shows live watts, not the rated number on the box.
- Plug the meter into the outlet, then the heater into the meter. Takes ten seconds.
- Turn the heater to the setting you actually use and read the watts after two minutes. Not the instant it switches on: wait for it to settle.
- Multiply by your rate. Watts ÷ 1,000 × your utility's cents-per-kWh (printed on your bill, usually under "supply charge" or "energy charge") = your real cost per hour.
- Watch it over a full cycle, not just the first two minutes. If the heater has a thermostat, the number will drop to zero for stretches once the room warms up: that's the actual average you want, not the peak.
That last step is the one that surprises people. A 1,500W-rated heater on its thermostat setting in a small closed bedroom can average far less than 1,500W over a full hour once the off-cycles are counted, well under the "High, continuous" number in the table below. Sizing and settings change the real answer more than the label ever will.
What does a space heater cost per hour, per night, per month?
The table below uses 18¢ per kWh: the approximate 2026 U.S. average residential rate reported by the U.S. Energy Information Administration. Your own rate might be lower (Nevada averages around 13¢) or much higher (Hawaii averages over 50¢); check your utility bill for the exact number, then scale these figures up or down.
| Setting | Watts | Cost / hour | Cost / 8-hr night | Cost / 30-night month |
|---|---|---|---|---|
| High | 1,500W | $0.27 | $2.16 | $64.80 |
| Medium | 900W | $0.16 | $1.30 | $38.88 |
| Low / Eco | 400W | $0.07 | $0.58 | $17.28 |
Those "per-month" numbers assume the heater runs at that wattage continuously for 8 hours every night. In practice, a heater with a real thermostat spends a lot of that time drawing zero watts because the element has already reached target temperature and shut off, which is the entire subject of the next section.
Which four settings actually cut the bill without freezing the room?
None of these need a new product. They're settings and habits, and they're the difference between the "High, all night, every night" number above and what most careful users actually pay.
- Use the thermostat or eco mode, not manual High. A heater with a target temperature draws full wattage only until the room reaches it, then cycles on and off in short bursts to hold steady. Manual High never shuts off. This single switch is usually the biggest line item on the list.
- Zone heat with the door closed. A space heater only saves money when it lets you turn the central thermostat down while it heats the one room you're in. Run it on top of an unchanged central system and you've added a cost, not cut one. The U.S. Department of Energy's home heating and cooling guide (PDF) says you save about 1% on heating for each 1°F you set the thermostat back during an eight-hour period: that's the saving zone heating is supposed to unlock. Put the unit where its warmth reaches you, as the placement guide describes, and the room warms faster for the same watts.
- Put it on a timer or a smart plug schedule. Most bedroom use only actually needs the heater running the hour before bed and the hour before waking, not eight straight hours. A $10 mechanical timer or a smart plug removes the "I forgot it was on" cost entirely.
- Match the wattage to the room instead of defaulting to the biggest unit. A 400–600W heater in a small bedroom or office reaches target temperature and then just maintains it. A 1,500W unit in that same small room overshoots, cycles harder, and wastes the difference as unwanted heat you then have to air out. The small-room heater guide has a wattage-by-room-size table.
What about plug-in energy savers like StopWatt?
This question comes up once people start watching their heating bill, because the ads are everywhere: a small box that plugs into an outlet and promises a smaller electric bill. StopWatt is the best-known example this winter, and it is one of several devices in the same category.
It is easy to see the appeal. A box that costs around $40 to $50 is a simple purchase next to rearranging a room for zone heating, and anything that helps a bill go down deserves a fair look. I have not tested StopWatt or any similar device, so I will not give you a number for what it does: every home, every set of appliances and every utility rate is different, and results will be too.
What I can offer is a clean way to find out for yourself, the same five-minute wattmeter reading from the section above. Take a reading of an appliance with the device plugged in, then one with it unplugged, over the same number of minutes and with nothing else changed. Whatever difference you see is your own answer. If you are curious, it is a low-cost thing to try, and that test tells you exactly what it does in your home.
Whether or not a device like that ends up in your home, the settings above (thermostat, zone heating, a timer, right-sizing the wattage) cost nothing and work with every heater. Start there, and treat anything extra as a bonus.
Which type of heater is cheapest to run for the same warmth?
For the same wattage, every resistance-based portable heater (ceramic, fan-forced, oil-filled) converts essentially all of its electricity into heat, so the running cost per watt is identical between them. What actually differs is how evenly and how long that heat lingers, which changes how often the thermostat has to cycle the element back on.
A ceramic heater warms a small room within minutes, so you reach your temperature quickly and let the thermostat take over, while an oil-filled radiator warms more slowly and keeps radiating after the element shuts off. Either way, the bill follows the hours the element is on, not the type. I go through the tradeoffs between types in more depth, including when infrared is worth a slightly higher running cost, in the types section of the pillar guide, and the ceramic vs infrared comparison answers that one question in full. If you want to see a full review of a specific room heater, my full test notes on the Heatoor cover its specs, price and warranty.
Put together, the real cost picture looks friendly: a well-sized heater on a thermostat, in a closed room, on a timer, lands closer to the Low/Eco row of the table than the High row (usually $15–$25 a month rather than $65) and it gets there with settings you already own.
Frequently asked questions
How much does it cost to run a space heater for 8 hours?
At the 2026 U.S. average rate of about 18¢/kWh: roughly $2.16 on High (1,500W), $1.30 on Medium (900W), or $0.58 on Low/Eco (400W). A heater with a working thermostat costs less than these full-power numbers because the element cycles off once the room is warm.
Do space heaters use a lot of electricity?
A 1,500W heater draws about as much as a hair dryer or microwave, not "a lot" on its own. It only saves money compared to central heat when it lets you turn the whole-house thermostat down while it heats the one room you're using.
Is it cheaper to run a space heater or central heat?
A space heater is cheaper only if it replaces heating the whole house: i.e., you turn the central thermostat down and heat just the occupied room. Run it alongside an unchanged central system and it adds cost instead of cutting it.
What about plug-in energy savers like StopWatt?
They are sold as a small box that plugs into an outlet to help a bill go down. I have not tested one, so I do not promise a number. To see what one does in your home, take a wattmeter reading of an appliance with the device plugged in and again unplugged, over the same minutes. The settings above (thermostat, zone heating, a timer, right-sizing) work with or without one.
What's the cheapest heater setting to run?
A correctly-sized heater left on its thermostat or eco setting rather than manual High. It reaches target temperature and then draws power in short bursts instead of continuously, which is what actually lowers the real-world average wattage.
Does turning a space heater to a lower wattage setting actually save money?
Yes, immediately and proportionally: cost scales directly with watts. Dropping from 1,500W to 900W cuts the hourly cost by 40% for the same runtime, though the room takes longer to reach the same temperature.