Space Heater Running Cost Calculator

Estimate the monthly and yearly cost of running a space heater from its wattage, daily hours of use, thermostat duty cycle and your electricity rate.

Heater power rating

Hours used per day

h/day

Thermostat duty cycle

Electricity price

$per kWh

Days used per month

days

Heating months per year

months

Cost per month

$61.20

Average power draw while on: 1.5Rated kilowatts multiplied by the duty cycle.
Energy used per day: 12Kilowatt-hours consumed each day of use.
Energy used per month: 360
Cost per hour of use: $0.255
Cost per day: $2.04
Cost for the heating season: $306.00Monthly cost times the number of heating months entered.
Heat output while running: 5,118Electric heaters convert essentially all input power to heat: 1 W = 3.412 BTU/h.

Assumptions

Assumes electric resistance heating, which converts essentially 100% of input electricity into heat at the point of use.
Assumes a single flat electricity price per kWh; tiered, time-of-use and demand charges are not modelled.
Assumes the heater draws its rated wattage whenever the element is on; the duty cycle accounts for thermostat cycling.
Fan and control electronics draw is treated as included in the nameplate wattage.
The yearly figure simply multiplies the monthly cost by the number of heating months entered.

Built with AI from a visitor’s request · not yet reviewed

How this is worked out

The formula

kWh per day = (watts / 1000) x (duty cycle / 100) x hours per day
Cost per month = kWh per day x days per month x price per kWh
Cost per hour = (watts / 1000) x (duty cycle / 100) x price per kWh
Heat output (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 on the heater or its label. Most plug-in heaters are 750 W or 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 switched-on time the element actually draws full power. Use 100% for no thermostat, 50-70% if it cycles off once the room is warm.a percentage · from 1 to 100 · defaults to 100
Electricity price: Your all-in rate from your utility bill, including delivery charges and taxes.in dollars · from 0 to 2 · defaults to 0.17
Days used per month: Number of days per month the heater is used at this rate.from 1 to 31 · defaults to 30
Heating months per year: Used only for the seasonal/yearly estimate.from 1 to 12 · defaults to 5

What you get back

Cost per monthmain answer
Average power draw while on: Rated kilowatts multiplied by the duty cycle.
Energy used per day: Kilowatt-hours consumed each day of use.
Energy used per month
Cost per hour of use
Cost per day
Cost for the heating season: Monthly cost times the number of heating months entered.
Heat output while running: Electric heaters convert essentially all input power to heat: 1 W = 3.412 BTU/h.

What this assumes

Assumes electric resistance heating, which converts essentially 100% of input electricity into heat at the point of use.
Assumes a single flat electricity price per kWh; tiered, time-of-use and demand charges are not modelled.
Assumes the heater draws its rated wattage whenever the element is on; the duty cycle accounts for thermostat cycling.
Fan and control electronics draw is treated as included in the nameplate wattage.
The yearly figure simply multiplies the monthly cost by the number of heating months entered.

About this calculator

What this calculator does

Electric space heaters are simple, cheap to buy, and surprisingly expensive to run. This calculator converts a heater's wattage into kilowatt-hours and then into money, so you can see what an evening of extra warmth actually costs.

Enter the heater's nameplate wattage (printed on the label or in the manual — typically 750 W on low and 1500 W on high), how many hours a day you switch it on, and your electricity price per kilowatt-hour. Use the all-in rate from your bill, not just the energy-supply portion, since delivery charges and taxes are also billed per kWh.

The duty cycle matters

A thermostatic heater does not draw full power the whole time it is on. Once the room reaches the set temperature, the element cycles off and only kicks back in when the air cools. A heater set to a modest temperature in a well-insulated room may run only 40–60% of the time. Set the duty cycle to 100% for a heater with no thermostat or one running flat out, and lower it to reflect cycling. This single number can halve or double your estimate, so it is the main source of uncertainty here.

How to read the results

The headline figure is the monthly cost at the usage pattern you entered. The cost-per-hour figure is handy for quick decisions — for example, whether it is cheaper to heat one room for an evening than to run central heating. All electric resistance heaters are essentially 100% efficient at the point of use, so a 1500 W ceramic, oil-filled, or infrared heater costs exactly the same per hour at the same setting; only heat pumps beat that. Results are estimates and ignore tiered or time-of-use pricing.

Frequently asked questions

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

A 1500 W heater running continuously uses 1.5 kWh per hour. At $0.17 per kWh that is about $0.26 per hour, or roughly $2.04 for an 8-hour day. At $0.30 per kWh it rises to $0.45 per hour. If the thermostat cycles the element off half the time, halve those numbers.

▸Where do I find my price per kilowatt-hour?

Divide the total amount of your electricity bill by the kilowatt-hours billed. That gives your true all-in rate including delivery, fixed-charge amortisation and taxes, which is usually noticeably higher than the advertised supply rate.

▸Are some space heaters cheaper to run than others?

Not at the same wattage. Ceramic, oil-filled, quartz-infrared and fan heaters all turn electricity into heat with the same effectiveness. Differences come from how they distribute heat and how well their thermostats and timers reduce running time — that is what the duty cycle input captures.

▸Should I use the low or high setting?

The setting changes the wattage, not the efficiency. A 750 W setting costs half as much per hour as 1500 W but takes longer to warm the room, so total energy for the same comfort is similar. Run this calculator twice with different wattages to compare.

▸Is a space heater cheaper than my central heating?

It can be if you heat just one occupied room and turn the main system down. But per unit of heat, electricity is usually more expensive than natural gas, and a heat pump delivers 2–4 units of heat per unit of electricity, so a resistance heater is rarely the cheapest way to heat a whole home.

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.