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Space Heater Running Cost Calculator

Estimate what a space heater costs to run 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.

W
h/day
%
days
$per kWh
months
Cost per month
$61.20
Total power draw
1.5
Cost per hour of element run time
$0.255
Energy used per day
12
Cost per day
$2.04
Energy used per month
360
Cost for the heating season
$244.80
Cost per week (at this daily use)
$14.28
Assumptions
  • Assumes an electric resistance heater, where power drawn equals heat delivered (100% conversion at the point of use).
  • Uses the nameplate wattage; actual draw varies slightly with voltage and heater setting.
  • Duty cycle is applied to the hours the heater is switched on, modelling thermostat cycling.
  • Electricity price is treated as a flat rate; time-of-use or tiered rates are not modelled.
  • Ignores standby, fan-only and control-electronics consumption (typically a few watts).
Built with AI from a visitor’s request · not yet reviewed

How this is worked out

The formula

kW = watts / 1000
kWh per day = kW x hours per day x (duty cycle / 100) x number of heaters
Cost per month = kWh per day x days per month x price per kWh
Cost per hour = 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 10000 · defaults to 1500
Hours used per day
How many hours the heater is switched on each day.from 0 to 24 · defaults to 8
Thermostat duty cycle
Share of the switched-on time the element actually draws power. Use 100% for constant output, 50-70% for thermostat cycling.a percentage · from 1 to 100 · defaults to 100
Days used per month
A number.from 1 to 31 · defaults to 30
Electricity price
All-in delivered rate from your bill, including supply and delivery charges.in dollars · from 0 to 2 · defaults to 0.17
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
Total power draw
Kilowatts drawn while the element is on.
Cost per hour of element run time
Energy used per day
Kilowatt-hours per day.
Cost per day
Energy used per month
Kilowatt-hours added to your monthly bill.
Cost for the heating season
Cost per week (at this daily use)

What this assumes

  • Assumes an electric resistance heater, where power drawn equals heat delivered (100% conversion at the point of use).
  • Uses the nameplate wattage; actual draw varies slightly with voltage and heater setting.
  • Duty cycle is applied to the hours the heater is switched on, modelling thermostat cycling.
  • Electricity price is treated as a flat rate; time-of-use or tiered rates are not modelled.
  • Ignores standby, fan-only and control-electronics consumption (typically a few watts).

About this calculator

What this calculator does

Electric space heaters are simple energy converters: essentially all the electricity they draw becomes heat, so their running cost depends only on how much power they pull and how long they pull it. This calculator turns the wattage on the label into kilowatt-hours and then into money using your own electricity rate.

How to use it

Enter the heater's wattage (1500 W is the maximum for a standard North American 120 V outlet; European heaters are often 2000 W). Enter the hours per day it is switched on, then set the duty cycle. This is the part most estimates get wrong: a thermostatically controlled heater in a room that has reached temperature only fires for part of the time. If the heater runs flat out on high, leave duty cycle at 100%. If it cycles on and off, 50-70% is realistic. Finally enter your electricity price per kWh — use the all-in figure from your bill (energy plus delivery charges divided by total kWh), not just the supply rate.

Where it is approximate

Results are exact arithmetic on the numbers you supply, but real use varies. Actual draw can differ a few percent from the nameplate rating, low/medium settings draw less, and the duty cycle changes with outdoor temperature, insulation and thermostat setting. Fan-only and oscillating modes add a few watts. For heat pumps or oil-filled radiators with variable output, use the average power you observe on a plug-in energy meter rather than the nameplate value.

Frequently asked questions

▸How much does a 1500 W heater cost per hour?

A 1500 W heater uses 1.5 kWh for every hour it runs at full output. At $0.17 per kWh that is about 25.5 cents an hour, or roughly $2.04 for an 8-hour day. Multiply 1.5 by your own rate to get your figure.

▸What duty cycle should I use?

If the heater has no thermostat, or you run it on high in a cold or draughty room, use 100%. In a well-insulated room where the thermostat clicks off regularly, 50-70% is typical. The only way to know precisely is to measure with a plug-in energy monitor over a day.

▸Are some electric heaters cheaper to run than others?

Among resistance heaters — ceramic, oil-filled, infrared, fan — no. All convert electricity to heat at essentially 100%, so a 1500 W heater of any type costs the same per hour. Differences come from how quickly they warm you (infrared heats people directly, so you may run it less) and from thermostat quality. Heat pumps are genuinely different: they can deliver 2-4 units of heat per unit of electricity.

▸Is a space heater cheaper than turning up central heating?

Sometimes. Heating one occupied room with a 1500 W heater while lowering the whole-house thermostat can cut costs, especially if your central system runs on expensive electric resistance heat. But if you have a gas furnace, gas is usually far cheaper per unit of heat than electricity, so running several space heaters typically costs more.

▸Why does my bill rise more than this calculator predicts?

Common reasons: the heater runs more hours than assumed, the duty cycle is higher in cold snaps, extra usage pushes you into a higher tariff tier, or the marginal delivered rate is above your average rate. Re-run the calculation with your top-tier rate to see the worst case.

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.