Heating, ventilation and air conditioning, or HVAC, systems perform three general functions in your home, depending on the type of system. HVAC systems make your home cooler, warmer and less humid. When you compare types of residential HVAC systems, you can more effectively choose which system, or combination of systems, is the best fit for your home.
Like furnaces, air conditioners serve only one task: air conditioners cool your home. And, like heat pumps, air conditioners move heat from inside your home to outdoors, lowering the indoor temperature. The main components of an air conditioning system, similar to the components of a heat pump system, include a compressor and an evaporator.
Air conditioning systems circulate a refrigerant fluid between the compressor and evaporator, converting the fluid at times into a liquid, and at other times a gas, pulling heat from the air inside your home in the process. As the heat leaves the air, the temperature lowers, which provides the cooling effect. Condensation, a secondary effect of removing heat from the air, also pulls moisture from the air. For this reason, air conditioned-air will have less moisture in it than untreated air.
In contrast to air conditioners and furnaces, which can perform only one task, heat pumps can both lower and raise the temperature inside your home. Like all types of residential HVAC systems, heat pumps use fans to move air through your home’s duct system. They also use an outdoor condenser unit with an indoor air handler.
To cool your home, heat pumps move heat from the air inside your home to the outdoors, so that the air remaining is at a lower temperature. During cold weather, heat pumps perform the opposite function, moving heat from outdoors to inside the home. This may seem counterintuitive, since the amount of heat in the air outside during winter months may seem negligible, but heat pumps are able to extract heat efficiently even from air that is a relatively low temperature.
Furnaces perform a complementary task to that of air conditioners, raising the temperature in your home by first generating heat and then distributing the heat through the air ducts. Your furnace may share the same ducts that your air conditioner uses, but it’s an entirely different system.
Furnaces can generate heat in several says, such as by burning natural gas or propane, using electricity to heat wire, or burning fossil fuels. In contrast with heat pumps, which pull existing heat from the air, furnaces create the heat, which can make them less energy-efficient than heat pump systems.