Space heater running cost

Estimate what an electric space heater costs to run per hour, day, week, month and year from its wattage, how long you run it and your electricity price.

Calculator

Appliance type

Used as the name in your comparison. It does not fill in any values.

Power

Rated input power from the label or manual. Appliances that cycle on and off use less on average.

Hours of use per day

On a day the appliance is used. Up to 24.

Days of use per week

Up to 7.

Effective power (%)

Your own assumption. 100% means full rated input for every hour entered. Lower it only if you know the unit cycles off.

Electricity price per kWh

From your bill or supplier. Use the price per kWh, for example 0.15.

Currency

Changes the currency symbol only. No exchange rates are applied.

How to find your price on your bill

Where your bill shows them, add up the charges billed per kWh, such as supply (or generation) and delivery. These are the charges that grow when an appliance runs.
Leave out fixed monthly charges, such as a customer or service charge. They generally stay the same however much electricity you use.
If the price is in cents, divide by 100: 15.5¢ per kWh is 0.155.
Only a total amount and total kWh? Dividing the amount by the kWh gives a rough all-in average. Because it includes fixed fees and taxes, it may overestimate the extra cost of running an appliance.
If your price changes by time of day or with how much you use, enter the price that applies to most of your use.

For comparison, the U.S. Energy Information Administration publishes average electricity prices by state. Your own bill gives a closer estimate.

Fill in the fields above to see your estimate.

Estimated results

Fill in the fields to see the estimated energy use and cost.

How to estimate the cost

Energy (kWh) = watts × hours ÷ 1,000, and cost = energy (kWh) × your price per kWh. One hour of use costs the heater's watts ÷ 1,000 × your price. A day of use multiplies that by the hours you run it, a week by the days you use it, a year is the week × 365 ÷ 7 and an average month is the year ÷ 12. The U.S. Energy Information Administration explains how electricity is measured: a watthour is one watt used for one hour and a kilowatt is 1,000 watts, so 1,000 W for one hour is 1 kWh.

Example (illustrative only)

A 1,500 W heater used 2 hours a day, 7 days a week, at full power, priced at $0.20 per kWh. The $0.20 is an example price, not a current U.S. average rate, so use the price from your own bill.

Per hour: 1,500 W ÷ 1,000 = 1.5 kWh, costing $0.30.
Per day of use: 1.5 kWh × 2 hours = 3 kWh, costing $0.60.
Week: 3 kWh × 7 days = 21 kWh, costing $4.20.
Average month: 1,095 kWh ÷ 12 = 91.25 kWh, costing $18.25.
Year: 21 kWh × 365 ÷ 7 = 1,095 kWh, costing $219.00.

The month and year assume use every week of the year. If you run the heater only in colder months, multiply the weekly cost by your weeks of use.

Why your actual cost can differ

Your electricity price. Prices vary by utility and plan, and some plans change the price by time of day or by how much you use.
Runtime. Cost rises in direct proportion to the hours the heater is switched on.
Thermostat cycling. A heater with a thermostat switches its heating off once the room reaches the set temperature, so it may draw full power for only part of the time it is on. The calculator starts at 100% effective power, which gives an upper-end estimate. Lower it only if you have a reason, such as readings from a plug-in energy monitor. No typical percentage is suggested, because it depends on the room, insulation, outdoor temperature and setting.
Power setting. If your heater has more than one setting, use the wattage for the setting you use, if the label or manual lists it.

Using the calculator

Enter the heater's rated power from the label or manual, in watts (W) or kilowatts (kW).
Enter the hours you run it on a day of use and the days you use it each week.
Enter your price per kWh. On your bill, add up the charges billed per kWh, such as supply and delivery, and leave out fixed monthly charges. If the price is in cents, divide by 100: 15.5¢ is $0.155. Open “How to find your price on your bill” under the price field for more detail.
Read the cost per hour, per day of use, week, average month and year, then add the heater to your comparison to see it on your dashboard.

For other appliances, use the appliance energy cost calculator. To convert between watts, hours and kWh, use the kWh calculator. The methodology explains every formula and rounding rule.