Space Heater Running Cost Calculator
Estimate what a space heater costs to run per hour, day, month and heating season from its wattage, hours of use and your electricity rate.
Space Heater Running Cost Calculator: with the default inputs, cost per month is $61.20.
Nameplate wattage. Most plug-in heaters are 750 W (low) or 1500 W (high).
Hours the heater is switched on each day.
Share of switched-on time the element actually draws power. Use 100% for no thermostat, 50-70% once a room is warm.
All-in rate from your bill, including delivery charges and taxes.
Use 30 for a typical month, or fewer if you only heat on some days.
How many identical heaters run on this schedule.
Months per year you run the heater on this schedule.
- Cost per hour of use
- $0.255
- Energy per day
- 12Kilowatt-hours used each day the heater runs.
- Cost per day
- $2.04
- Energy per month
- 360Kilowatt-hours added to your bill each month.
- Cost per heating season
- $306.00
- Energy per heating season
- 1,800
- Heat output at full power
- 5,118BTU per hour delivered while the element is on (electric resistance heat is ~100% efficient).
Assumptions
- Electric resistance heating is treated as ~100% efficient, so watts drawn equal heat delivered.
- A flat electricity price is applied; tiered and time-of-use rates are not modeled.
- Duty cycle is a user estimate of the share of on-time at full power.
- Standby/fan-only power draw and inrush effects are ignored.
- BTU output is shown at full rated power, not derated by duty cycle.
How this is worked out
The formula
kW = Watts / 1000 x (Duty cycle / 100) x Number of heaters kWh per day = kW x Hours per day Cost per month = kWh per day x Days per month x Price per kWh Cost per season = Cost per month x Season months BTU/h = Watts x 3.412
Open How it’s calculated above to see this worked through with your own numbers.
What you enter
- Heater power rating
- Nameplate wattage. Most plug-in heaters are 750 W (low) or 1500 W (high).from 50 to 10000 · defaults to 1500
- Hours used per day
- Hours the heater is switched on each day.from 0 to 24 · defaults to 8
- Thermostat duty cycle
- Share of switched-on time the element actually draws power. Use 100% for no thermostat, 50-70% once a room is warm.a percentage · from 5 to 100 · defaults to 100
- Electricity price
- All-in rate from your bill, including delivery charges and taxes.in dollars · from 0 to 2 · defaults to 0.17
- Days used per month
- Use 30 for a typical month, or fewer if you only heat on some days.from 1 to 31 · defaults to 30
- Number of heaters
- How many identical heaters run on this schedule.from 1 to 20 · defaults to 1
- Length of heating season
- Months per year you run the heater on this schedule.from 1 to 12 · defaults to 5
What you get back
- Cost per monthmain answer
- Cost per hour of use
- Energy per day
- Kilowatt-hours used each day the heater runs.
- Cost per day
- Energy per month
- Kilowatt-hours added to your bill each month.
- Cost per heating season
- Energy per heating season
- Heat output at full power
- BTU per hour delivered while the element is on (electric resistance heat is ~100% efficient).
What this assumes
- Electric resistance heating is treated as ~100% efficient, so watts drawn equal heat delivered.
- A flat electricity price is applied; tiered and time-of-use rates are not modeled.
- Duty cycle is a user estimate of the share of on-time at full power.
- Standby/fan-only power draw and inrush effects are ignored.
- BTU output is shown at full rated power, not derated by duty cycle.
About this calculator
What this calculator does
Electric space heaters are simple energy consumers: essentially every watt they draw becomes heat, so the cost is just power multiplied by time multiplied by your electricity rate. Enter the heater's wattage (printed on the nameplate or in the manual), how many hours a day you run it, and the all-in price you pay per kilowatt-hour, and this tool returns the cost per hour, per day, per month and across a whole heating season.
How to use it
- Power rating: use the setting you actually use. A 1500 W heater on "low" is usually 750 W.
- Duty cycle: a thermostatic heater blasts at full power until the room warms, then cycles. If you leave it at 100%, you get the worst-case bill. In a reasonably insulated room, 40–70% is a realistic long-run average.
- Electricity price: take your total monthly bill divided by kWh used, not just the energy-supply rate, so delivery charges and taxes are included.
Where it's approximate
The energy math is exact; the uncertainty is all in the duty cycle. Actual cycling depends on room size, insulation, outdoor temperature and your thermostat setting. Tiered or time-of-use rates also mean your marginal price may be higher than your average price — if you are near a tier boundary, enter the higher tier rate. Fan-only or eco modes draw less than the nameplate rating, and oil-filled radiators feel gentler but cost exactly the same per kilowatt-hour of heat delivered.
Frequently asked questions
▸How much does a 1500 W heater cost per hour?
At 100% duty cycle it uses 1.5 kWh per hour. Multiply by your rate: at $0.17/kWh that is about $0.26 per hour, or roughly $2.04 for an 8-hour day and about $61 for a 30-day month. Halve those figures if the thermostat cycles the element off about half the time.
▸What duty cycle should I use?
Use 100% if the heater has no thermostat or you run it flat out. If it maintains a set temperature in a normal insulated room, 40–70% is typical over a full evening. Colder outdoor temperatures and drafty rooms push the number toward 100%.
▸Are oil-filled or infrared heaters cheaper to run?
Not per unit of heat. Any electric resistance heater converts nearly all electricity to heat, so 1500 W costs the same regardless of the technology. Differences come from how much you actually run them — infrared heats you directly and oil radiators keep radiating after cycling off, which can lower effective run time.
▸Is a space heater cheaper than central heating?
Sometimes. Heating one occupied room with a space heater while turning the whole-house thermostat down can save money, but electricity per kWh usually costs 3–4x natural gas per equivalent unit of heat, and heat pumps deliver 2–4 kWh of heat per kWh of electricity. Compare using your own rates.
▸Where do I find my real electricity price?
Divide the total amount of your electricity bill by the kilowatt-hours listed on it. That captures supply, delivery, fixed-charge spread and taxes, and is usually higher than the headline energy rate.
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.