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Saving energy at home:
Electric space heaters

Beware of inflated claims and prices

Advertisements promise that certain models of electric space heaters will save 50 percent on heating costs. Many may wonder if this and other claims are true.

In fact, depending on how portable heaters are used, consumers actually can see their total energy costs go up. And promises of whole-house comfort from portable electric space heaters are exaggerated.

Let's look into the real capability of portable heaters and review how they should be used to obtain maximum payback.

A watt is a watt

Some dealers are selling what is basically a 1,500-watt electric space heater for $250, $300, $400, and even more. Packaged in furniture-like wooden boxes, or wood-looking plastic, what's inside is still a 1,500-watt heater—capable of putting out the same amount of heat at the same cost as a 1,500-watt milk house heater that costs $25.

The only feature of an electric heater that affects the amount of heat the unit can generate is wattage. No matter how elaborate the cabinet that holds it, electric heating is the same. And buyers need to understand how the electric heater works or risk succumbing to a pretty package.


If you're going to heat with electricity, a better investment is a heat pump or an off-peak electric system.
Both are far more economical to operate than electric space heaters.

Electricity is efficient

All electric heating is 100 percent efficient. That means the energy that goes into an electric heater will come out as heat. No energy is wasted.

The only electric heating that is more efficient are heat pumps (air-source or geothermal). Because they use electric energy to capture heat and move it rather than to make heat, they operate at higher efficiencies.
(Air-source heat pumps are 200 percent efficient at certain temperatures, and geothermal heat pumps operate at more than 300 percent efficiency.)

These options aside, whether it is a radiant, convection, or fan-forced electric heater—and whether it cost $25 or $500—it is going to operate at 100 percent efficiency.

The best heater also may be the least expensive to buy

Consumers looking for an electric space heater and tempted by advertising claims are advised to do some research. Consumer Reports published a review of space heaters in October 2007 that showed these higher-priced models disappointed—with one model providing “only fair temperature control and ease of use,” and another, equipped with an air purifier, providing “lackluster temperature control, cleaned the air poorly, and lacks an overheat-protection feature.” This same article shows superior performance and recommended safety features in a model that sells for about $60.

Know operating costs

So, how much will an electric space heater cost to operate? You can use the following formula to calculate how much it will cost to operate a 1,500-watt space heater (or any other electric equipment):

Watts x hours of use ÷ 1,000 x cost per kilowatt-hour = cost of operation

This means that if a 1,500-watt heater ran 24-hours at a rate of 7.57 cents a kilowatt-hour, the cost would be $2.73 a day (1,500 x 24 ÷ 1,000 x $0.0757). For a month that would amount to $81.76 added to the electric bill of the average customer.

Portable heaters are intended for spot heating

Spot, or zone, heating is what portable electric heaters were designed to do. If a portable heater is used in one area and the thermostat for the main heating system is lowered, energy savings are possible. However, if a portable heater is used in one room and the main heating system also is running, savings are not likely to be achieved.

Additionally, to achieve savings a portable heater must operate with a thermostat so it doesn't run continually. Heaters with multiple output settings let you choose the lowest setting that keeps a room comfortable. Temperature control is key to saving energy.

Select for safety

When buying and using an electric space heater, follow these safety guidelines.

  • Look for a product that carries an Underwriters Lab (UL) label.
  • Select one that automatically shuts off if tipped and that has protective casing over the heating element to avoid the potential for burns.
  • Avoid using an extension cord but, if one is needed, be sure it has at least 12-gauge wire.
  • Select the proper wattage so your portable electric space heater doesn't overload your electrical wiring and create a fire safety issue.
  • Select a model that has a thermostat so it doesn't run all the time.
  • Never allow an electric space heater to run when you are out of the house or asleep.

If you're going to heat with electricity and want to make a better long-term investment, other options, such as a heat pump system or an off-peak electric system, are far more economical to operate than electric space heaters.

If you have questions about safely operating a portable electric space heater or about how its use will affect your electric service statement, please call Otter Tail Power Company's Idea Center at 800-493-3299.

This article first appeared in Lake and Home Magazine, Feb/Mar 2009.