Q: Is it really more economical to use electric space heaters where the people are than to heat the whole house?

Asked by Mary Fahnestock, ’70, Oxford, Ohio

The U.S. Department of Energy estimates that more than 50 percent of energy used in American homes goes to heating and cooling. So could the energy generated from heating technology be used more wisely? The answer is: "It depends," says Dr. John Haymaker, assistant professor of civil and environmental engineering at Stanford. "It depends on . . . how warm [it is outside], where is the house, how efficient are the heaters, et cetera." With the recent cold snaps across the country, efficiently delivering warmth to your home has become a priority, so let's examine the heating systems and their tradeoffs in order to see what is right for you.

A central heat system is used to heat all parts of your home and is also the most popular type of heating in the United States. Central heating is usually powered by electricity or gas, and less commonly by heating oil, coal or wood in some regions. Of these energy resources, electricity is the most expensive energy commodity for the majority of U.S. households, making it the least economic option. And when coal or natural gas are used to produce that electricity—as is the case for 40 percent of American homes—about 70 percent of the fuel energy is lost during conversion to electricity and even more can dissipate on the way to your house. Electrical heat isn't just expensive for you; it carries a very high carbon footprint as well.

Portable space heaters are small heating devices that lack transfer ducts but rely on the same types of energy. These heaters may require a combustion mechanism or simply utilize electricity. Combustion heaters are serious fire hazards and can produce dangerous gases into the air as a result of the burning process itself.

The most cost-effective electric heater utilizes a radiant heat method. Here, the machine emits infrared radiation directed towards objects located in its line of vision. These "smart" heaters tend to be very efficient in their heat allocation because they do not emit it continuously into the whole space. Therefore, if you are not planning on moving around in your room (because you are sleeping or working at your desk), or if you have company seated around the dinner table, the need to tip the central thermostat upward falls away.

However, directly heating your house is only part of the equation for staying warm. A key point to keep in mind regardless of the heating style you choose is insulation. Proper insulation can lower your household's energy consumption by more than 20 percent, which is to say that you can be a lot warmer for a lot less money. Seal and insulate ducts and holes especially in places like your attic, garage and basement. In addition, don't forget to shut windows completely and check to make sure that your doors are closed (including lowering the hatch on the doggy door). Lastly, your system is only as efficient as its weakest part—make sure to replace faltering equipment, such as cracked belts and loose connections.

But what about an often-overlooked option in our society? When the temperature increase desired is not very big, simply putting on an additional layer can save you money you never expected to save over the course of that month. Wool is one of the best and longest used fabrics for staying warm.

So put on a sweater, as my fellow columnist says, and remember, if you are still cold, portable space heaters can indeed be more economical for the purpose of heating a small portion of the home, while gas-powered central heating can be most efficient for keeping your whole house warm and cozy.

Marina Oster is a PhD student in the biosciences.