Space Heater Running Cost Calculator
Estimate what a space heater costs per month from its wattage, hours used per day, thermostat duty cycle and your electricity price per kWh.
Space Heater Running Cost Calculator: with the default inputs, cost per month is $61.20.
Nameplate wattage on the heater or its label (most portable heaters are 750–1500 W).
How many hours the heater is switched on each day.
Days in the billing month you actually use the heater.
All-in rate from your bill: total electricity charges divided by kWh used.
Share of the 'on' time the element actually draws full power. Use 100% for no thermostat, 50–70% for typical cycling.
Multi-setting heaters draw a fraction of the rated wattage on lower settings.
Electricity cost for the month at the settings above.
- Average power draw while on
- 1,500Rated watts adjusted for the power setting and thermostat cycling.
- Energy used per day
- 12Kilowatt-hours added to your bill each day.
- Energy used per month
- 360
- Cost per hour of use
- $0.255
- Cost per day
- $2.04
- Cost for a 4-month heating season
- $244.80Same usage pattern repeated for four winter months.
- Cost if used all year
- $734.40
Assumptions
- Assumes a resistive electric heater, where electrical input equals heat output (100% efficiency at the plug).
- Uses a flat electricity price; time-of-use, tiered or demand rates are not modelled.
- Power setting factors are approximations (1, 2/3, 1/2, 1/3 of rated wattage).
- Duty cycle is user-supplied, not derived from room size or outdoor temperature.
- Ignores standby draw of displays or controls, which is negligible.
How this is worked out
The formula
kWh per day = (rated watts x setting factor x duty cycle) / 1000 x hours per day Monthly cost = kWh per day x days per month x price per kWh Hourly cost = average kW x price per kWh
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 portable heaters are 750–1500 W).from 50 to 5000 · defaults to 1500
- Hours used per day
- How many hours the heater is switched on each day.from 0 to 24 · defaults to 8
- Days per month
- Days in the billing month you actually use the heater.from 1 to 31 · defaults to 30
- Electricity price
- All-in rate from your bill: total electricity charges divided by kWh used.in dollars · from 0 to 2 · defaults to 0.17
- Thermostat duty cycle
- Share of the 'on' time the element actually draws full power. Use 100% for no thermostat, 50–70% for typical cycling.a percentage · from 5 to 100 · defaults to 100
- Power setting
- Multi-setting heaters draw a fraction of the rated wattage on lower settings.High / full rated wattage · Medium (about 2/3 power) · Low (about 1/2 power) · Eco (about 1/3 power)
What you get back
- Cost per monthmain answer
- Electricity cost for the month at the settings above.
- Average power draw while on
- Rated watts adjusted for the power setting and thermostat cycling.
- Energy used per day
- Kilowatt-hours added to your bill each day.
- Energy used per month
- Cost per hour of use
- Cost per day
- Cost for a 4-month heating season
- Same usage pattern repeated for four winter months.
- Cost if used all year
What this assumes
- Assumes a resistive electric heater, where electrical input equals heat output (100% efficiency at the plug).
- Uses a flat electricity price; time-of-use, tiered or demand rates are not modelled.
- Power setting factors are approximations (1, 2/3, 1/2, 1/3 of rated wattage).
- Duty cycle is user-supplied, not derived from room size or outdoor temperature.
- Ignores standby draw of displays or controls, which is negligible.
About this calculator
What this calculator does
Electric resistance heaters are simple to cost out: every watt they draw becomes heat, so the bill depends only on power, run time and your electricity rate.
Enter the heater's rated wattage (printed on the label or back panel — 1500 W is the standard maximum for a US plug-in unit, 2000–3000 W for many 230 V models), the hours per day it runs, the number of days in the month you use it, and your price per kWh. For the price, don't just use the energy charge from your tariff sheet — divide your total monthly electricity bill by the kWh on it, so delivery fees and taxes are included. That usually gives a noticeably higher and more honest number.
Two optional controls make the estimate realistic. The power setting scales a multi-setting heater down to roughly a half or a third of rated wattage. The duty cycle accounts for a thermostat: once a room reaches temperature, the element switches off and on, so a heater that is "on" for 8 hours may only draw full power for 4–6 of them. Set duty cycle to 100% for a heater with no thermostat or one running flat out in a cold, drafty space.
Where it's approximate
Real duty cycle depends on insulation, outdoor temperature and your target setting, so treat the result as a range rather than a precise figure. Fans, oil-filled radiators and ceramic heaters of the same wattage cost exactly the same to run — marketing claims about "efficient" resistance heaters don't change the physics. Heat pumps are the exception: they deliver 2–4 units of heat per unit of electricity and can't be modelled here.
Frequently asked questions
▸How much does a 1500 W heater cost to run per month?
At 8 hours a day for 30 days with no thermostat cycling and electricity at $0.17/kWh, that's 360 kWh and about $61 a month. With a thermostat cycling at a 60% duty cycle it drops to roughly $37. Change the price field to your own rate for a local answer.
▸Where do I find my real price per kWh?
Take the total amount of your electricity bill (including supply, delivery, fixed fees and taxes) and divide it by the kWh consumed that month. This all-in rate is often 20–50% higher than the headline energy rate and is the right number for marginal usage estimates.
▸Are oil-filled or ceramic heaters cheaper to run?
Not at the same wattage. All electric resistance heaters convert essentially 100% of the electricity into heat. Differences come from how well the thermostat matches your comfort level and whether you can heat a smaller area — not from the heating element type.
▸What duty cycle should I use?
For a well-insulated room where the heater quickly reaches the set temperature, 40–60% is typical. In a drafty garage, a poorly insulated room or in very cold weather, the element may run nearly continuously, so use 85–100%.
▸Is a space heater cheaper than turning up central heating?
Sometimes. Heating one room with 1500 W can beat running a whole-house furnace, but if your central system is a heat pump it may deliver the same heat for a third of the electricity. Compare this monthly cost against your normal heating bill before switching.
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.