Air Source Heat Pumps

The most common type of heat pump is the air-source heat pump, which transfers heat between your house and outside air. An air-source heat pump can provide efficient heating and cooling for your home, especially if you live in a warm climate. If you heat with electricity, a heat pump can trim the amount of electricity you use for heating by as much as 30%–40% and can deliver one-and-a-half to three times more heat energy to a home than the electrical energy it consumes. This is possible because a heat pump moves heat rather than converting it from a fuel, like in combustion heating systems. Due to technological advances, the efficiency and performance of today's air-source heat pumps is 150% - 200% greater than those available 30 years ago.

High-efficiency heat pumps also dehumidify better than standard central air conditioners, resulting in less energy usage and more cooling comfort in summer months. However, the efficiency of most air-source heat pumps as a heat source drops dramatically at low temperatures, generally making them unsuitable for cold climates, although there are systems that can overcome that problem.

For homes without ducts, air-source heat pumps are also available in a ductless version called a mini-split heat pump. In addition, a special type of air-source heat pump called a "reverse cycle chiller" generates hot and cold water rather than air, allowing it to be used with radiant floor heating systems in heating mode.

Although air-source heat pumps can be used in nearly all parts of the United States, they do not generally perform well over extended periods of sub-freezing temperatures. In regions with sub-freezing winter temperatures, it may not be cost effective to meet all your heating needs with a standard air-source heat pump.

However, new systems with gas heating as a backup are able to overcome this problem. There is also a "Cold Climate Heat Pump" which shows promise, but is currently facing manufacturing problems. In addition, the "Reverse Cycle Chiller" claims to be able to operate efficiently at below-freezing temperatures.

Source Material: US Dept. of Energy

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