Space Heater Running Cost Calculator
Estimate what a space heater costs per hour, day and month from its wattage, hours of use, thermostat duty cycle and your electricity rate.
Space Heater Running Cost Calculator: with the default inputs, cost per month is $61.20.
Nameplate wattage on the heater or its label. Most plug-in heaters are 750–1500 W.
Hours the heater is switched on each day (not necessarily heating the whole time).
All-in rate from your bill: total bill divided by kWh used gives the most accurate figure.
Share of the switched-on time the element actually draws power. Use 100% for no thermostat, 50–70% for typical thermostat cycling.
Used only for the seasonal total.
- Electricity used per month
- 360Kilowatt-hours added to your bill each month.
- Cost per hour on
- $0.255
- Cost per day of use
- $2.04
- Cost per week (7 days of use)
- $14.28
- Cost for the heating season
- $244.80
- Cost if used year-round
- $734.40
- Heat output
- 5,118Full-power heat output in BTU per hour (1 W = 3.412 BTU/h).
Assumptions
- Assumes an electric resistance heater where 100% of the electricity consumed becomes heat (COP = 1); heat pumps deliver 2–4x more heat per kWh.
- Uses the nameplate wattage as the full-power draw; the duty cycle scales average consumption.
- Assumes a single flat electricity price per kWh, with no tiered, demand or time-of-use charges.
- Fan and control electronics are ignored (a few watts at most).
How this is worked out
The formula
kW = watts / 1000 x number of heaters x duty cycle kWh per month = kW x hours per day x days per month Cost per month = kWh per month x price per kWh Cost per hour = kW x price per kWh BTU/h = total watts x 3.412142
Open How it’s calculated above to see this worked through with your own numbers.
What you enter
- Heater power rating
- Nameplate wattage on the heater or its label. Most plug-in heaters are 750–1500 W.from 1 to 10000 · defaults to 1500
- Hours used per day
- Hours the heater is switched on each day (not necessarily heating the whole time).from 0 to 24 · defaults to 8
- Days used per month
- A number.from 1 to 31 · defaults to 30
- Electricity price
- All-in rate from your bill: total bill divided by kWh used gives the most accurate figure.in dollars · from 0 to 2 · defaults to 0.17
- Thermostat duty cycle
- Share of the switched-on time the element actually draws power. Use 100% for no thermostat, 50–70% for typical thermostat cycling.a percentage · from 5 to 100 · defaults to 100
- Number of heaters
- A number.from 1 to 20 · defaults to 1
- Length of heating season
- Used only for the seasonal total.from 1 to 12 · defaults to 4
What you get back
- Cost per monthmain answer
- Electricity used per month
- Kilowatt-hours added to your bill each month.
- Cost per hour on
- Cost per day of use
- Cost per week (7 days of use)
- Cost for the heating season
- Cost if used year-round
- Heat output
- Full-power heat output in BTU per hour (1 W = 3.412 BTU/h).
What this assumes
- Assumes an electric resistance heater where 100% of the electricity consumed becomes heat (COP = 1); heat pumps deliver 2–4x more heat per kWh.
- Uses the nameplate wattage as the full-power draw; the duty cycle scales average consumption.
- Assumes a single flat electricity price per kWh, with no tiered, demand or time-of-use charges.
- Fan and control electronics are ignored (a few watts at most).
About this calculator
What this calculator does
Electric resistance heaters are simple to cost out: every watt they draw becomes a watt of heat, so the only things that matter are the wattage, how long the heater runs, and what you pay per kilowatt-hour.
Enter the nameplate wattage (usually printed on a label near the plug or on the base), the hours the heater is switched on each day, how many days a month you use it, and your electricity price. The calculator converts watts to kilowatts, multiplies by running hours to get kilowatt-hours, and multiplies by your rate to get the cost per hour, day, week, month and season.
Duty cycle matters
A thermostatically controlled heater does not draw full power the whole time it is on — it cycles the element off once the room reaches temperature. A 1500 W heater running at a 60% duty cycle only uses 0.9 kWh per hour on average. Set the duty cycle to 100% for a heater with no thermostat or one running flat-out in a cold, draughty room, and 40–70% for a well-insulated room that reaches its set point.
Where it's approximate
Real duty cycle varies with outdoor temperature, insulation, room size and thermostat setting, so treat the result as a good estimate rather than a bill. If your utility uses tiered or time-of-use pricing, enter the marginal rate that applies to the extra usage — that is usually higher than your average rate. Fan-only or low-setting modes draw less than the nameplate figure; enter the lower wattage in that case.
Frequently asked questions
▸How much does a 1500 W space heater cost per hour?
At full power it uses 1.5 kWh per hour. At 17 cents per kWh that is about 25.5 cents an hour, or roughly $2.04 for an 8-hour day. With a thermostat cycling at 60% duty, the average drops to about 15 cents an hour.
▸What duty cycle should I enter?
If the heater has no thermostat, or you run it on high in a cold space that never reaches the set point, use 100%. In a small, reasonably insulated room that warms up and holds temperature, 40–70% is typical. If you are unsure, run the numbers at both 100% and 60% to bracket the likely cost.
▸Is a space heater cheaper than central heating?
Sometimes. Heating one occupied room with a 1500 W heater while turning down whole-house heat can save money, but electric resistance heat costs more per unit of heat than natural gas or a heat pump in most regions. Compare your electricity rate against your gas rate per unit of delivered heat before switching.
▸Where do I find my price per kWh?
Divide the total amount on your electricity bill (including delivery charges and taxes) by the kilowatt-hours used that month. That all-in figure reflects what extra usage really costs better than the headline energy rate alone.
▸Do oil-filled, ceramic and infrared heaters use different amounts of electricity?
No — at the same wattage they all consume the same electricity and produce the same amount of heat. They differ in how the heat is delivered (radiant vs convected) and how quickly a room feels warm, which can change how long you run them and therefore your real duty cycle.
How this calculator was made
A visitor asked for: “Cost to run a space heater for a month from its wattage, hours used per day and the price per kilowatt-hour”. An AI model wrote the formulas as a declarative spec, our engine checked that every expression parses and evaluates, and the math above runs deterministically in your browser. It hasn’t been reviewed by a person yet — check the assumptions and the How it’s calculated panel before relying on it.