The use of Geothermal Heat Pumps(or GHP’s) date back to the early to mid 20th century. A GHP uses the constant temperature from the earth as a source for conditioning air inside your home rather than converting the exterior air temperature around your home. This allows the heat pump system to be extremely energy efficient because the starting temperature point that your heat pump is converting is closer to the desired temperature within your home. Subterrain ground temperatures in Columbia SC are somewhere around 68° F, whereas the outside air temperature can vary from around 100°F in the summer and 30°F in the winter. Heat pumps are very complex but the principle is to take a substance, such as air or water, and extract the heat or cold from it. Since most people keep their home closer to 68° than 100° or 30°, it allows the system to convert the temperature with less strain and electricity. Feel free to comment if you know any more about this system.
There are several variations of heat pumps and they seem to increase with price depending on the energy efficiency. For instance, GHP’s are more expensive because there are more components to install but are said to have longevity.
A dual-source heat pump uses both the outside air temperature and the ground source (water) temperature together and is a hybrid system. It is less energy efficient, louder, and less expensive than a geothermal heat pump.
An air-source heat pump is less to install but not as efficient as a dual-source heat pump or GHP. It does not take advantage of the ground temperature.