A heat pump is an energy efficient home heating system that can also cool. Almost half of the average home’s energy use goes toward heating, so making the switch to a heat pump is one of the biggest steps you can take to significantly reduce your carbon footprint. The fact that heat pumps are powered by electricity sourced from low-carbon sources further lowers your impact.
The way a heat pump works is by moving thermal energy from a cool space to a warm one using a refrigeration cycle. The cool space is usually the ground, water or outdoor air, and the warm space is often your indoor living space. The system transfers heat through a series of pumps, fans and coils to keep the temperatures in the two spaces consistent. Heat pumps are incredibly efficient, and their performance is measured by something called the coefficient of performance (COP), which indicates how much energy they produce per unit of electrical power used.
Most residential heat pumps are air-source, which means they look a lot like your central air conditioner. There’s an outdoor unit with aluminum fins and coils that release or absorb heat, connected to an indoor unit with a blower by a refrigerant line filled with fluid that transports the heat between the units. The fan in the indoor unit blows air over these coils and through ductwork that distributes it throughout your house, and a compressor in the outdoor unit uses electricity to compress the refrigerant and boost its temperature.
In some cases, heat pumps can be combined with other forms of supplemental or backup heating systems to better handle colder climates. This can be done either in a hybrid configuration with a gas furnace or by using an electric heater in addition to the Heat Pump, which is known as a ground-source system.
Some heat pumps are also available in a direct-drive model, which does away with the compressor and instead relies on a motor to drive a fan and a series of coils that circulate warm or cool air through your home. These systems are typically less expensive than ducted air-source models, but they can still require a substantial upfront investment.
The biggest limitation of a heat pump is its inability to extract sufficient heat from cold environments, which means that it requires more supplemental energy in cold climates than does a traditional gas furnace. However, manufacturers are working on ways to improve this limitation.