How Much Does It Cost to Run a Space Heater?
A 1,500 W space heater costs about 28¢ an hour to run at the US average electricity rate. See the cost per day, month and season in your state.
A standard 1,500-watt space heater running at full output costs about 28¢ per hour at the US average electricity rate of 18.44¢/kWh. Run it eight hours a day and you are looking at roughly $1.55 a day, or $47 a month — before you account for the fact that almost no heater actually runs at full output.
That last part is where most cost estimates go wrong. A thermostat-controlled heater cycles on and off once the room reaches temperature, so it typically draws full power only 50–80% of the time it is switched on. The calculator below models that directly, and prices it at your state's actual rate rather than a national average that may be nowhere near what you pay.
- Per month
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- Per day used
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- kWh / year
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Space heater cost by hours used
These figures assume a 1,500 W heater with a 70% duty cycle — a realistic average for a thermostat-controlled unit in a room that is not badly insulated. A heater fighting a draughty room will run closer to 100%.
| Usage | kWh/day | Per day | Per 30 days | Per season |
|---|---|---|---|---|
| 2 hr/day | 2.10 | 39¢ | $11.62 | $46.5 |
| 4 hr/day | 4.20 | 77¢ | $23.23 | $92.9 |
| 6 hr/day | 6.30 | $1.16 | $34.85 | $139 |
| 8 hr/day | 8.40 | $1.55 | $46.47 | $186 |
| 12 hr/day | 12.60 | $2.32 | $69.70 | $279 |
| 24 hr/day | 25.20 | $4.65 | $139 | $558 |
The "per season" column assumes a 120-day heating season, roughly November through February in most of the country.
What it costs in your state
Electricity rates vary by more than four times across the US, so the same heater used identically costs wildly different amounts depending on where you plug it in.
| State | Rate | Cost | vs US avg | |
|---|---|---|---|---|
| Idaho | 12.35¢ | $124 | −61.4 | below average |
| Texas | 16.44¢ | $166 | −20.2 | below average |
| Florida | 15.17¢ | $153 | −33.0 | below average |
| Ohio | 19.52¢ | $197 | +10.9 | near average |
| Pennsylvania | 21.55¢ | $217 | +31.3 | above average |
| New York | 29.93¢ | $302 | +116 | above average |
| California | 33.25¢ | $335 | +149 | above average |
| Hawaii | 52.00¢ | $524 | +338 | above average |
Full table: electricity rates by state.
Why every space heater is 1,500 watts
Walk down the heater aisle and nearly every box says 1,500 W. That is not coincidence or laziness — it is the electrical code.
A standard US household outlet sits on a 15-amp, 120-volt circuit. That circuit can carry 1,800 watts in theory, but the National Electrical Code limits a continuous load to 80% of the breaker rating: 12 amps, or 1,440 watts. Manufacturers round that to a marketed 1,500 W and stop there. Anything claiming more from a normal plug is either a 240 V appliance, or it is counting watts creatively.
"Energy-efficient space heater." There is no such thing. Every electric resistance heater — ceramic, infrared, oil-filled, quartz, the $400 one in a wooden cabinet — converts essentially 100% of the electricity it draws into heat. Two 1,500 W heaters running for one hour produce identical heat and cost identical money. Marketing that implies otherwise is describing comfort, not efficiency.
Real differences between heaters come from three things that have nothing to do with watts per hour:
- Thermostat quality. A heater that holds temperature accurately cycles off sooner. This is the only meaningful efficiency lever, and it is a duty-cycle effect, not an output effect.
- Where the heat goes. Radiant and infrared heaters warm objects and people directly, so you feel warm at a lower air temperature. Convection and oil-filled heaters warm the air, which then leaks out of the room.
- Thermal mass. An oil-filled radiator keeps releasing heat after it cycles off. Same electricity, smoother delivery.
Space heater vs central heating: when it actually saves money
The pitch for a space heater is zone heating — warm the one room you are in instead of the whole house. That works, but only under a condition most people skip.
Run the numbers per million BTU of delivered heat. Electric resistance at 18.44¢/kWh works out to about $54 per million BTU. Natural gas at around $1.20 a therm through a 90% efficient furnace comes to about $13 per million BTU. A modern heat pump lands between the two, usually $15–25.
So a space heater saves money only if adding it lets you turn the central thermostat down meaningfully. Heating one room with electricity while the furnace still holds the rest of the house at 70°F is the most expensive possible combination — you are paying the premium rate for heat you did not subtract from anywhere.
Zone heating pays off if you drop the whole-house thermostat by 6–8°F and heat a single occupied room. A 1°F setback saves roughly 1–3% of heating energy over an 8-hour period, so an 8°F setback on a gas furnace usually more than covers one space heater running in the room you are actually in.
How a space heater compares to other heating
| Heating method | Watts | Duty | kWh/yr | Cost/yr |
|---|---|---|---|---|
| Electric furnace | 15,000 W | 35% | 6,300 | $1,162 |
| Space heater (portable) | 1,500 W | 70% | 1,008 | $186 |
| Electric baseboard heater | 1,500 W | 60% | 1,260 | $232 |
| Oil-filled radiator | 1,500 W | 55% | 990 | $183 |
| Heat pump (whole home) | 3,500 W | 50% | 3,150 | $581 |
| Ductless mini-split | 1,200 W | 60% | 1,080 | $199 |
| Electric blanket | 100 W | 50% | 48 | $8.85 |
The electric blanket line is not a joke. Heating a body costs a fraction of heating the air around it, and for sedentary evening use it substitutes for a lot of space-heater runtime.
Five ways to cut the cost
- Turn the main thermostat down first. Without this the heater is a pure addition to your bill, not a substitute.
- Use the low setting. Most heaters offer 750 W and 1,500 W. Low halves the draw, and in a small or well-sealed room it often holds temperature perfectly well.
- Close the door and block the gap. Duty cycle is everything. A door snake on a bedroom door does more for your bill than any heater upgrade.
- Never run it in an empty room. Radiant heat in particular is worthless with nobody there to absorb it. A plug-in timer or a model with a built-in one pays for itself in a season.
- Check for an old thermostat. A heater with a crude bimetallic thermostat overshoots by several degrees, wasting every degree of the overshoot.
Frequently asked questions
How much does it cost to run a space heater for 24 hours?
A 1,500 W heater at a 70% duty cycle uses about 25.2 kWh over 24 hours, costing roughly $4.65 at the US average of 18.44¢/kWh. At California's 33.25¢ it is about $8.38; at Idaho's 12.35¢, about $3.11.
Is it cheaper to run a space heater or central heat?
Per unit of heat, central gas heating is about four times cheaper. A space heater only saves money if you use it to lower the whole-house thermostat by several degrees. If your central heat is electric resistance, a space heater in one room is genuinely cheaper than heating the whole house.
Do oil-filled radiators use less electricity?
Not per hour — a 1,500 W oil-filled radiator draws exactly as much as any other 1,500 W heater. It can use less over a full evening because the oil stores heat and keeps radiating after the element cycles off, which lowers the duty cycle. The saving is modest, typically 10–15%.
What size space heater do I need?
Roughly 10 watts per square foot for a room with average insulation and an 8-foot ceiling. A 150 sq ft bedroom needs about 1,500 W; a 100 sq ft office is comfortable on the 750 W setting. Oversizing does not cost more to run — the thermostat simply cycles off sooner.
Do space heaters use a lot of electricity?
Yes, by household standards. At 1,500 W a single heater draws more power than a refrigerator, a TV, a laptop and every light in an average home combined. It is one of the few things you can plug into a normal outlet that can add $50 or more to a single month's bill.
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