I came across a website that gives a great description of heat pumps, how they work, and why they are more efficient. Here’s the link for it.
Most Americans are accustomed to heating systems that generate heat using fossil fuels, wood, or electricity. But heat pumps don’t create heat, they move heat. Here’s how the process is explained on that website:
Heat pumps function similarly to refrigerators or air conditioners, which take warm air from one space and send it to another. In the winter, a heat pump transfers heat from the outdoors inside and, in the summer, it reverses this process.
There are two main types of heat pumps, and both can function as space heaters or coolers and as water heaters.
A ground-source (or “geothermal”) heat pump sends a mixture of water, antifreeze, and/or a refrigerant through a network of pipes buried below the frost line. As the liquid passes through the pipes, it absorbs the earth’s approximately 55-degree heat. The liquid is then drawn up into a compressor, which heats it further, creating a vapor. The heat pump then distributes the warm air through ducts or tubes throughout your home. In the summer, the heat pump reverses the process, taking warmth out of the house and transferring it to the earth.
An air-source heat pump extracts heat from the air rather than from the ground. It functions the same way, but because air temperature, unlike earth temperature, can get very cold, it has more work to do bringing up the temperature. As with a ground-source heat pump, a reversing valve inside the heat pump allows the same unit to function as an air conditioner in the summer. At right is an air source heat pump that was retrofitted into a ducted forced air heating/cooling system of one of my current listings in Golden.