When it comes to heating your home, a forced air furnace is not your only option.
Heat pumps — which have been used since the 1940s — also offer a viable way to keep your home warm and are growing in popularity, especially in states with moderate climates. Here are the main differences between a heat pump and a furnace.
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How heat is generated
Forced air furnaces use flame to heat air and a fan to push that heated air through ducts and out of floor vents in your home. Older model furnaces were notoriously inefficient, but newer models can be up to 98 percent energy efficient, meaning 98 percent of the energy taken is used to produce or distribute heat. Forced air heating uses what's known as intermediary fluid — usually air, steam or hot water — to provide heat.
Heat pumps, meanwhile, actually pump heat from outside air, rather than increasing its temperature using a flame. These pumps rely on what's known as a refrigeration cycle — the same process that cools your refrigerator, only in reverse. They use an outdoor compressor made of copper tubing and aluminum fins to draw in heat from the air and compress it. Then, a refrigerant evaporates the heat into a gas, transfers it to a coil inside the house, condenses the heat back into a liquid and distributes it around your home. It's important to note that heat pumps can be air source (drawing heat from the air outside your home) or ground source (drawing heat directly from the ground). Ground-source models are more expensive.
How heat pumps are powered
Furnaces can be powered by oil, natural gas or electricity. Oil is the least efficient method, although some providers have developed alternatives known as biodiesel, which cause less pollution than standard heating oil. Natural gas and electric furnaces are both common options in modern homes, though both pose the risk of fire, either from the burning natural gas or an electrical arc needed to generate a flame. Carbon monoxide (CO), which is produced when natural gas or oil is burned, also poses a potential risk. If not vented properly, a furnace can pump CO into the air, which displaces oxygen and can cause permanent brain damage or death.
A heat pump, meanwhile, does not require fuel but instead runs on electricity. This doesn't pose the same risk of fire or CO poisoning and can be used both for heating in winter and cooling in summer. While the same kinds of risks may not exist, the U.S. Department of Energy does note that many pumps suffer from improperly installed compressors, leaky ductwork or incorrect refrigerant levels. The compressors can also be noisy, meaning they should be located well away from a window or door. Installing a heat pump is not a task to undertake on your own; always hire an HVAC professional to ensure the work is correct and complete.
Where heat pumps work best
In parts of the country where electricity rates are low, a heat pump can provide a cheaper alternative to a standard, fuel-based furnace. But it's important to consider the outside climate as well. In temperatures under 40 degrees Fahrenheit, compressing heat from outside air becomes problematic, and a system of electric or gas-fired resistance coils (essentially a mini-furnace) kicks in to provide heating for your home. These are not as efficient as a traditional furnace. Furnaces, meanwhile, can't effectively cool hot summer air and, without the addition of an air conditioner — which is actually a one-way heat pump — won't be able to cool your home.
Ultimately, the choice between a furnace and heat pump comes down to your climate, the cost of your electricity and gas and which type of heating you prefer.
Editor's note: This is an updated version of an article that was originally posted on April 19, 2013.
Did you choose a heat pump for your home? Tell us why in the comments.