Air-source heat pumps are widely used in mild climates where the units don't have to work inordinately hard. In very cold climates, you probably want a combustion heater that can crank out hordes of Btu in a short time. But if you're in a mild climate, an air-source heat pump is probably one of your best choices. They connect to the existing ductwork, like any other heater or air-conditioner, and they accomplish both heating and cooling in the same package (refer to the earlier section "The (Very) Basics of Geothermal Heating and Cooling" for details). It's rarely the case that an air-source heat pump is used with a radiant heating system, but it can be done if you decide it's worth the extra cost (which it may very well be; see Chapter 17 for more details on radiant systems).
As you consider an air-source heat pump, keep these things in mind:
I The heat source, which is air, is free and limitless. No increase in energy costs will ever raise the price of air.
I Although air-source heat pumps require an expensive upfront investment in equipment, they're the least expensive type of heat pump to install. And because installation is relatively easy, you can get a wider variety of qualified installers to give you a bid. Competition is always a good thing.
Air-source heat pumps for a residential home cost more than other options for heating and cooling. The payback comes in terms of lower power bills.
I The technology is mature and getting better all the time. You can rest assured that if you get new equipment, the quality will be good in terms of both design and implementation.
I Air-source heat pumps are better for some climates than for others. If you live in a climate that requires heating and cooling in approximately equal amounts, an air-source heat pump is a viable option. If you need a lot more heating than cooling, a stove system is a better bet (with portable air conditioners, if need be). In moist, cold weather, air-source heat pumps don't do very well and the efficiency suffers. You may need some backup heating means if the temperature is less than 10°F for more than eight hours.
The best bet is to use a gas stove in conjunction with an air-source heat pump. The heating cycle of a heat pump is less efficient than the cooling cycle, and a gas stove (or other type of stove) has the advantage of allowing you to heat locally. This is inherently more efficient than a heat pump that powers your entire home.
1 Air-source heat pumps can be very noisy — fans make noise with most HVAC systems, but when you add the compressor you get some real rock 'n' roll.
1 Air-source heat pumps need abundant electricity. If your power goes off, you're not heating or cooling.
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