If you use a portable electric space heater to provide supplemental heat for your home, you may want to consider how much it will cost to operate before you plug it in. This does not have to be a mystery. You can calculate that cost with some simple information about the heater and a copy of your electric bill.

## Units of Energy

Electricity is measured and sold by the kilowatt-hour. This is a measurement of power that takes into account the amount of energy and the time frame over which it is consumed, similar to the measurement of horsepower in motors. A kilowatt-hour is equivalent to 1,000 watts of electricity, used over a period of one hour.

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## Calculating Heater Energy Use

Most electric appliances have the wattage of electricity they use stamped on the appliance, or on an information plate attached to the appliance. Electric heaters may have two or three different settings, and the information plate or owner's manual should give the wattage at each setting. To calculate the power use in kilowatt-hours, multiply the wattage that the heater uses by the number of hours per day that it will operate, and divide that amount by 1,000. A 1,500 watt electric heater operated for eight hours per day will use 12 kilowatt-hours of electricity daily.

## Cost of Use

Multiply the number of kilowatt-hours that your heater uses per day by the price you pay for each kilowatt-hour of electricity. This price varies depending on your location, but you should be able to find it on your electric bill. At 12 cents per kilowatt-hour, a 1,500 watt heater used for 8 hours per day will cost $1.44 per day, or $43.20 per month. Some utilities offer a lower rate for electric power during certain times of the day, typically at night, so your price may be lower when the heater is used then.

## Metering Options

Portable household meters measure how much electricity most plug-in appliances use. Some devices plug directly into the wall, and you then plug the appliance into the device. The meter measures the amount of watts that the appliance has consumed since it was plugged in, and the total time that the usage has been measured, to calculate kilowatt-hours. This will help measure the electrical use of appliances where the wattage is unknown.