Choosing a high efficiency electric heater.

High efficiency electric heaters do not exist, in terms of "heat per dollar". I often see electric heaters advertised as "high efficiency", but one of the Laws of Thermodynamics dictates that any watt hour of electricity will produce the same amount of heat as any other watt hour, no matter what kind of device is used to "burn" the electricity. You can only plug your heaters into one electric power company, so all watt hours cost you the same price on any particular day. Thus the term, "heat per dollar".

The amount of heat produced by one watt hour of electricity is 3.413 B.T.U.'s. Period. This fact holds true for every thing from a little coffee cup heater to the electric furnace that heats your whole house, as long as the only source of energy is electricity. It would seem that heat pumps and reverse cycle air conditioners are an exception to the rule, but they are not. Heat pumps actually do produce more useful heat than the electricity they use would account for because they are not just burning electricity, they are literally pumping heat from somewhere else, into the house. A heat pump is a high efficiency heater that runs on electricity, but it is not an electric heater. It is quite literally, a pump.

The smallest heat pump I know of (9,000 B.T.U.'s) produces about the same amount of heat as two and a half, one thousand watt electric space heaters, and costs about $300. Based on those numbers, the decision point is about one thousand hours. If your needs are temporary, you can buy two electric heaters for less than $50, and they will run for more than a thousand hours before they use up $250 in electricity. That is, the other $250 you did not pay for a heat pump. If you can see that you will need more than a thousand hours of heat in a few years, a heat pump is the "high efficiency" heater that makes sense. (These numbers only apply if you are considering one or two small heaters. The calculations for a whole house are entirely different.)

An electric water heater might be labeled as high efficiency because it has good insulation. The heat lost through its insulation is a very small percentage of the energy used to heat the water, but it still produces 3.413 B.T.U.'s of heat for every watt hour of electricity it uses. A cheap water heater can radiate enough heat into the utility room to cost you $75 a year on your electric bill. Putting a layer of R-13 fiberglass insulation around it ($12) can cut that loss to $14 per year. That is what I call more heat per dollar, but it is not because the water heater is more efficient at using electricity. It is because proper insulation is far more efficient than a lack of proper insulation.

You might save that $14 per year by using "tankless" water heaters. The difficulty with tankless water heaters is that they require about 146 amps of 240 volt electricity to produce 4 gallons of hot water per minute (based on heating 60 degree water to 120 degrees). The cost to upgrade the electric service to a house, by one or two hundred amps, is around a thousand dollars. Two tankless heaters and their installation is easily $500. Technically, the tankless system does deliver more heat per dollar than traditional water heaters that do exactly the same job, and you can show a net profit in about 110 years if nothing breaks and needs to be repaired.

A gas fired tankless water heater might be a lot cheaper to install because flammable fuels can easily deliver five times the amount of heat normally available with electricity (in a residential situation), but this guide is about electric heaters so I will say no more about this, except that I don't work with flammable fuels and have no idea what it costs to install that kind of service.

An electric space heater might be labeled as high efficiency because it is rather small, and so it produces a lot of heat for its size. It is not more efficient in terms of heat per dollar than any other electric space heater because a little nine inch square ceramic heater produces the same 3.413 B.T.U.'s per watt hour as an infrared light bulb, a long, low, baseboard heater, or an oil filled space heater that looks like an old fashioned steam radiator. As far as heat per dollar, small and hot is exactly equal to big and warm.

Personally, I prefer a larger space heater because they do not get as hot in any one place as a small heater, and so reduce the risk of causing a fire. In addition, the cycling from room temperature to "very hot" will make the smaller heater suffer more mechanical stresses than a large heater, and it will probably break sooner because of that.

These numbers are based on 9 cents per kilowatt hour and 2006 prices.

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