Heat pumps can warm or cool homes efficiently by pulling heat from different sources like the air or the ground. Ground-based heat pumps work the best. There are different types based on how they work, like compression, absorption, or adsorption. Choosing a low-temperature heat source is crucial for planning. Heat pumps are generally good for the environment, but some older types used harmful substances. Newer systems are better for the ozone layer. Using more renewable energy for electricity makes heat pumps even better for the environment over time.