Whether or not a heat pump will save you money on energy bills depends on a number of factors, including the type of fuel prevalent in your area, your climate, and the amount of insulation and other energy-efficient features built into your home. The general wisdom is this: If you have natural gas available, it probably makes sense for you to use it for heating and cooling with a conventional forced-air heating and air-conditioning system. Natural gas, needed for a gas furnace, has traditionally been a more efficient, less expensive fuel than electricity—though this is changing.

But in the Northeast or other regions where fuel-oil or electric-resistance heat is more the norm, a heat pump can realize substantial savings. Although electric-resistance heating is much less expensive to install than a heat pump, the heat pump can deliver 1 1/2 to 2 1/2 times more heat with the same amount of energy, depending on climate, the house, and the particular system.

Heat pumps are most effective at saving energy when in the heating mode. The problem with an air-source heat pump in a cold climate, however, is that a house needs more heat as the temperature outside goes down, but the heat pump works less efficiently at lower outdoor temperatures.

The right way to decide the most appropriate form of heating and cooling for your home is to do an economic analysis based on a system’s purchase price and efficiency, the cost of your fuel, and your home’s heating/cooling load requirements. Keep in mind that if you’re replacing an existing forced-air furnace and air conditioner with a heat pump, the ductwork may need to be replaced, too. Heat pumps generally require larger ducts.