Calculator · space heater
What does a space heater cost to run?
A plug-in electric heater turns its electrical input into heat, so its cost depends on two things: the watts it draws and how long it draws them. Enter the wattage from its label, the hours it's on and your price per kWh.
Updated November 1, 2026 · Edited by Carlos Gil, publisher · formulas and rate presets checked against the sources below
Short answer
- A plug-in heater's cost is its wattage × hours on × your price per kWh: 1,500 W for 4 hours a day for 30 days is 180 kWh, or $27.00 at 15¢.
- Resistance heaters of the same wattage cost the same per hour; a thermostat lowers the cost by switching the heater off once the room is warm.
Your numbers
Example valuesThese are example inputs so you can see how it works. Replace them with your own.
Many plug-in heaters list their maximum on a label; if yours has a low setting, use the watts for the setting you use.
30 for about a month.
With its thermostat, a heater cycles off once the room warms up. 100% assumes it never cycles off; try a lower share to see a range.
The price of one more kWh, in cents. Find yours with the price per kWh calculator; the per-kWh rate is better than the all-in average for valuing savings.
Or use a published Florida rate for the next kWh, before taxes and local fees (sources):
Result
EstimateFrom example values$27.00 for 30 days
- Electricity used over 30 days
- 180.0 kWh
- Per day
- 6.00 kWh · $0.90
- Per year at the same pattern
- 2,190 kWh · $328.50
- 365 days of the same daily use. Real use usually varies by season.
1,500 W ÷ 1,000 × 4 h × 100% × 30 days = 180.0 kWh; × 15.00¢ = $27.00
How this is calculated
kWh = watts ÷ 1,000 × hours on per day × share of time at full power × days × number of units. Cost = kWh × your price per kWh. With the example (1,500 W, 4 hours a day, 30 days, 18¢/kWh): 1.5 kW × 4 h × 30 = 180 kWh, and 180 kWh × $0.18 = $32.40.
Label wattage is a maximum. Appliances with a thermostat or compressor (heaters, refrigerators, air conditioners, dehumidifiers) switch on and off, so they draw full power only part of the time. That's what the "share of time" field adjusts. We don't guess it for you. For appliances with an ordinary plug, a plug-in power meter gives the real average; space heaters are the exception, because they should be plugged directly into a wall outlet.
Use the per-kWh rate, not your all-in average: fixed monthly charges don't change when an appliance runs less. Percentage-based taxes and local fees are not included.
Example: 1,500 W for 4 hours a day for 30 days is 180 kWh. At 15¢ per kWh that's $27.00. Halve the hours and the cost halves. Every electric resistance heater of the same wattage costs the same to run per hour; designs differ in how they spread the heat, not in the electricity they turn into heat.
A 1,500-watt heater on FPL and JEA rates
Monthly cost for 30 days at full power, using the price of the next kWh on each utility's current residential rate, before taxes and local fees. Which column applies depends on whether your whole bill is above or below 1,000 kWh, because both utilities charge more per kWh above that line. A thermostat that cycles the heater off lowers every figure.
| Hours a day | kWh a month | FPL, first 1,000 kWh (12.26¢) | FPL, above 1,000 kWh (14.26¢) | JEA, first 1,000 kWh (12.79¢) | JEA, above 1,000 kWh (14.68¢) |
|---|---|---|---|---|---|
| 1 hour | 45 | $5.52 | $6.42 | $5.76 | $6.61 |
| 2 hours | 90 | $11.03 | $12.83 | $11.51 | $13.21 |
| 4 hours | 180 | $22.06 | $25.66 | $23.02 | $26.42 |
| 8 hours | 360 | $44.13 | $51.33 | $46.04 | $52.85 |
Safety first
U.S. Fire Administration guidance
The U.S. Fire Administration advises plugging space heaters directly into a wall outlet (no extension cord or power strip), keeping them at least 3 feet from anything that can burn, and setting them on a flat, level surface. Read the guidance.
Always follow the heater manufacturer's instructions. This calculator estimates cost only; it isn't safety advice.
Comparing options: a heat pump moves heat rather than making it, so it typically delivers more heat per kWh than a resistance heater. Whether heating one room with a space heater costs less than heating the whole home depends on how much you lower the central thermostat while you do it. Check your bill to see your price per kWh.
Illustrative example: one heater, one cold month, two Florida bills
An invented 1,500 W heater, on 6 hours a day for 30 days, drawing full power 60% of that time as its thermostat cycles: 1.5 × 6 × 60% × 30 = 162 kWh. What it adds to the bill depends on the rest of your usage, because both utilities charge more per kWh above 1,000 kWh. Before taxes and local fees:
| Rest of the bill | FPL | JEA |
|---|---|---|
| 900 kWh, so the heater takes it to 1,062 | $21.08 | $21.89 |
| 1,200 kWh, already above 1,000 | $23.10 | $23.78 |
In the first row, 100 of the heater's kWh are priced at the lower rate and 62 at the higher one. In the second, all 162 are at the higher rate. Use the price that matches your own bills in the calculator above.
What a heater adds to your daily use
The example heater uses 5.4 kWh a day. EIA's 2024 average for a Florida residential customer works out to about 36.3 kWh a day, so a heater used like this adds roughly 15% to an average home's daily use. If your kWh per day rose by something like that in a cold month, the heater may explain it; put the two bills into the bill comparison to separate the extra use from billing days and price.
If your heater has a lower setting, the cost per hour falls in step with the watts: at half the watts, half the cost for each hour it draws power. It may take longer to warm the room, so compare by the hours it actually runs.
Estimating how long it really draws power
The share of time at full power is the number most people guess. Because the U.S. Fire Administration advises plugging space heaters directly into a wall outlet, we don't suggest putting a plug-in meter between the heater and the outlet. Instead:
- Bracket it. Run the calculator at 100% for the most it could cost, then at a lower share for a range. If even the upper figure is small, you have your answer.
- Use the heater's own display. If it shows when it's heating, note how often that is during a typical evening.
- Compare your usage. Divide the kWh on a bill by its billing days and compare with a similar bill from before you used the heater. JEA's bill shows 13 months of usage, and FPL's Energy Manager shows when, where and how your home uses energy. Weather and other changes affect this too, so treat it as a check rather than a measurement.
Other ways to lower winter heating cost
- Set the central thermostat back. The U.S. Department of Energy says you can save as much as 10% a year on heating and cooling by turning the thermostat back 7–10°F for 8 hours a day from its normal setting. With a heat pump, DOE advises doing this only with a thermostat designed for heat pumps.
- FPL On Call. Where it's offered, FPL lists a bill credit of $2.75 a month from November to March for central electric heat it may cycle off for up to 3 hours a day, $13.75 over a season. FPL says the program may not be offered in your area yet.
- JEA rebates. JEA's residential rebate list includes $50 for an HVAC tune-up and $50 for a smart thermostat. Check the terms on the rebates page before you count on either.
Mistakes that throw off a heater estimate
- The highest wattage for a lower setting. If you use the low setting, enter the watts for that setting.
- A month of use for a few cold weeks. Enter the number of days you actually ran it, not 30 by default.
- Every hour it's plugged in. Count the hours it's switched on, not the hours it sits in the outlet switched off.
- The lower tier price on a winter bill above 1,000 kWh. Check your bills: if they're above 1,000 kWh, the heater's kWh cost the higher price.
Frequently asked questions
How much does it cost to run a 1,500-watt space heater for an hour?
It uses 1.5 kWh in an hour at full power. At 15¢ per kWh that is 22.5¢ an hour; multiply 1.5 by your own price per kWh for your cost.
Do more expensive space heaters use less electricity?
Not per hour at the same wattage. Electric resistance heaters turn their electrical input into heat, so designs differ in how they spread the heat, not in how much electricity a given wattage uses.
Is a space heater cheaper than central heat?
It depends on how much you lower the central thermostat while you use it, and on your system. A heat pump moves heat rather than making it, so it typically delivers more heat per kWh than a resistance heater.
How do I use a space heater safely?
The U.S. Fire Administration advises plugging space heaters directly into a wall outlet, keeping them at least 3 feet from anything that can burn, and setting them on a flat, level surface. Follow the manufacturer's instructions too.
Why does my heater cost less than the calculator says?
If its thermostat cycles it off, it draws full power only part of the time. Lower the share-of-time field, or compare your daily kWh in your utility's usage tool on days with and without the heater. Don't put a meter or power strip between a heater and the wall outlet.
Sources
- U.S. Fire Administration (FEMA), portable heater fire safety · checked October 31, 2026
- FPL residential rates, October 2026 (PDF) · checked October 31, 2026
- JEA rates, including Electric Rates Definitions · checked October 31, 2026
- U.S. Energy Information Administration, Electric Sales, Revenue, and Average Price, Table 5.a (2024 data, released Oct 7, 2025) · checked October 31, 2026
- U.S. Department of Energy · checked October 31, 2026
- FPL On Call · checked October 31, 2026
- JEA residential rebates · checked October 31, 2026
- FPL Energy Manager · checked October 31, 2026
- JEA bill explanation · checked October 31, 2026