Knowing where household heat comes from is more important than many might think.

Different models of furnaces can determine what residents pay to stay warm. Having the facts can help consumers stay toasty for less.

The most fundamental difference between furnaces for renters is the fuel they consume. Gas furnaces operate at 95 percent efficiency, losing some of their heat through an exhaust chimney or flue, according to Ron Breese, owner of Breezy’s Heating & AC, 1016 Market St.

“If you have a gas furnace, you have an exhaust pipe, and that’s heat and air that you’re wasting,” Breese said.

Meanwhile electric furnaces, for which exhaust channels are unnecessary, are 100 percent efficient.

A gas furnace, however, is less expensive to operate than an electric. The cause of this is the lower price of gas, but this advantage may not be long-lived.

“Gas is cheaper to run, but with gas prices rising, pretty soon it’ll be a wash,” Breese said of the fuel-cost relationship.

Some apartments have combinations of forced-air heating, with which a central furnace heats and propels air through vents to deliver it around an apartment, as well as other methods, such as baseboard-heating, which uses long electric heaters placed where the wall meets the floor to radiate heat through a room.

“[Baseboard-heating is] great for when I just want to heat the bathroom for my shower in the morning,” said Mike Marchak, who rents a Mason Townhouse with both types of heaters.

Also, according to Breese, it’s more affordable than using the central furnace in that situation.

“If those vents are in the ceiling, there’s a strong chance they run through the attic, so you’re heating all that space as well,” Breese said. By using baseboard heating to warm specific areas of the apartment, renters can save the money it would cost to heat the entire house, and possibly more.