An air-source heat pump can provide very efficient heating and cooling for your home, especially in our hot humid climate. The U.S. Department of Energy offers a very good explanation of how a heat pump works and why it works so well in our region.
When properly installed, an air-source heat pump 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.
How They Work
A heat pump's refrigeration system consists of a compressor and two coils made of copper tubing (one indoors and one outside), which are surrounded by aluminum fins to aid heat transfer. In the heating mode, liquid refrigerant extracts heat from the outside coils and air, and moves it inside as it evaporates into a gas. The indoor coils transfer heat from the refrigerant as it condenses back into a liquid. A reversing valve, near the compressor, can change the direction of the refrigerant flow for cooling as well as for defrosting the outdoor coils in winter.
When outdoor temperatures fall below 25- 30°F, a less-efficient panel of electric resistance coils, similar to those in your toaster, kicks in to provide indoor heating. The efficiency and performance of today's air-source heat pumps is one-and-a-half to two times greater than those available 30 years ago. This improvement in efficiency has resulted from technical advances and options such as these:
• Thermostatic expansion valves for more precise control of the refrigerant flow to the indoor coil
• Variable speed blowers, which are more efficient and can compensate for some of the adverse effects of restricted ducts, dirty filters, and dirty coils
• Improved coil design
• Improved electric motor and two-speed compressor designs
• Copper tubing, grooved inside to increase surface area.
My advice is to make the most of your dollars you spend on your HVAC and invest in the savings that a heat pump can offer you.