Heat pumps draw heat energy from outdoor air using refrigerant to keep your home warm during the winter. In the summer, the cycle is reversed to expel heat from the home and cool the air. Unlike a standard furnace or air conditioner, heat pumps offer a high level of energy efficiency to keep utility costs low. An inverter, or variable-speed, heat pump maximizes efficiency and reduces energy lost during the refrigerant cycle.
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During a standard refrigerant cycle, the refrigerant travels continually between the compressor and condenser, transforming from liquid to gas depending on temperature. Once the air in the home reaches the temperature specified on the thermostat, this refrigerant cycle stops completely, restarting only when the home's temperature changes. Each time the cycle restarts, the system consumes energy to balance pressure and bring the refrigerant to the correct temperature before the heating or cooling process can begin.
In units with a variable-speed compressor, or inverter, the refrigerant cycle operates at different speeds depending on temperature and heating loads. By automatically adjusting the speed of the refrigerant, the inverter eliminates energy losses caused by stopping and starting.
Inverter heat pumps reduce cycling to keep your family more comfortable and to eliminate cold drafts. By minimizing energy lost during cycling, they also improve your home's overall energy efficiency and reduce energy consumption. This not only helps keep your heating and cooling bills in check but also protects the environment from the effects of air pollution and greenhouse gas emissions.
In some heat pumps, the inverter technology may also reduce operating noise and extend the life of the compressor and other system components.
Manufacturers often use the terms "variable speed" or "multispeed" to refer to heat pumps with built-in inverter technology. Consumers should be aware that these terms are also used to describe the heat pump blower. While variable-speed blowers offer advantages of their own, they are unrelated to variable-speed compressors.
Some inverter heat pumps also cost more than standard models and may require additional maintenance because of a more complex operating system.
Both ducted and ductless heat pumps may use inverter technology to improve energy efficiency. Ducted units work just like your air conditioner or furnace, transporting air to each room through a network of ducts. Ductless, or mini-split systems, include an outdoor compressor and indoor condenser connected by a series of tubes. The tubes carry refrigerant between the two units, eliminating the need for ducts.
Because inverter technology increases a heat pump's energy efficiency rating, many inverter uses qualify for federal and state tax credits. Before you buy, make sure the unit you're considering qualifies for these incentive programs. Despite manufacturer claims, not all Energy Star-certified units meet the required standards for federal and state tax credits.