How much does a space heater cost to run?

Convert the label into energy

Divide watts by 1,000 to get kilowatts. Multiply by hours used to get kilowatt-hours (kWh), the unit utilities bill for.

A transparent monthly example

At an illustrative $0.16 per kWh, 1.5 kW used for eight hours a day for 30 days is 360 kWh, or $57.60. Your rate, schedule, and calendar month may be different.

The thermostat may cycle off

A heater that reaches its set point may not draw full power every minute. Measure a representative period or model a duty cycle instead of treating the nameplate as a promise.

Safety: keep heaters clear of combustibles, plug them directly into a suitable wall outlet, and follow the manufacturer instructions. The estimate does not make an unsafe setup safe.

Low settings save less than they seem to

Many 1,500-watt heaters offer a lower setting, often around 750 watts. Halving the power halves the cost per hour, not necessarily the cost of keeping a room warm.

On a 750 W setting the heater uses 0.75 kWh an hour. If the room then takes twice as long to warm, or the heater runs twice as many minutes to hold the temperature, the energy used ends up much the same.

What actually reduces the cost is heating less space for fewer hours: warming the room you are in, turning the heater off when you leave, and keeping the door closed.

Compared with heating the whole home

A space heater only lowers the bill when it lets you keep the rest of the home cooler. Running it on top of normal heating adds to the bill.

Every electric resistance heater turns electricity into heat one for one, so a 1,500 W heater delivers the same heat whatever the brand or the marketing. The saving, when there is one, comes from turning the central thermostat down while one occupied room is heated.

To compare, put the heater estimate beside the heating portion of your own bills. If the central system is a heat pump, which moves heat rather than making it, the comparison can easily favor the central system.