We answer your questions about energy.

Q. I see lots of ads for electric heaters that promise to cut heating costs. How is that possible? I thought electric heat was an expensive way to heat a home.

A. Electric heat can be a more expensive way to heat an entire house if you’re talking about straight resistance heat, which is the same as the heating system in a toaster. But if you use resistance electric space heaters to heat only the room or rooms you use most, and turn down the heat in the rest of the house, you likely will heat for less. Try to keep the doors closed in the low-temperature rooms.

All electric space heaters are pretty much the same in terms of operating cost. They provide 3,413 British thermal units of heat for each kilowatt-hour consumed. Some space heaters use heat lamps for the heat, others convey the heat in oil-filled tubes, still others use ceramic to moderate the flow of heat so it’s more evenly dispersed. No matter the purchase price, they cost about the same to operate.

Q. My husband wants to buy an outside wood furnace from which the heat is piped to the house. The wood is free as long as he cuts it, but the furnace is expensive. Is this a good way to go?

A. If you’ve got ‘free’ wood and are willing to work to cut and split it, the cost to operate the wood furnace is pretty low. All you’re paying for is the electricity to run the fan or pump that delivers the heat to your house. Of course, the split wood does have a market value, in the neighborhood of $100 to $125 a cord. You could sell it.

The increasing interest in wood heat has some people worried. Scientists have long known that wood smoke contains carbon monoxide and cancer-causing chemicals. But research shows that wood smoke’s major ingredient — tiny particles of soot and liquid pollution — worsens heart disease and triggers asthma attacks.

In some communities, mostly in the West, 30 percent to 80 percent of the wintertime particle pollution is attributed to wood burning in the home. The attorneys general of Michigan, Connecticut, Maryland, Massachusetts, New Jersey, New York and Vermont petitioned the Environmental Protection Agency in August to set limits on emissions from outdoor wood boilers.

Q. I’ve seen ads that say you can save 1 percent of your heating bill for every 1 degree you turn down your thermostat. Other ads say you can save 3 percent. What’s right?

A. You will save 1 percent of your heating bill for every degree you dial down your thermostat for an 8-hour period. If you turn down the thermostat 5 degrees overnight, you’ll save 5 percent on your bill. If you dial down from 70 to 68 degrees permanently, you’ll save 6 percent on your bill (2 percent for each of three 8-hour periods). Combine the overall drop of 2 degrees with an additional nighttime drop of 5 degrees and you’ll cut 11 percent from your bill.

Anytime your furnace works less to replace the heat lost to the outside, you save money. So don’t be afraid to drop your thermostat to 55 or 60 degrees if you’re gone for the weekend, or to dial down a few degrees if you’ll be gone a few hours. It all adds up.