There are three types of heat pump systems.
You can get a water source heat pump, geothermal heat pump or an air source heat pump.
A water based heat pump is basically how it sounds. You need it installed by a body of water in order to run. A geothermal heat pump has the outdoor air compressor buried underground to access the heat temperatures. Think of in the wintertime how cold the air is. The air under the soil is actually quite a bit warmer, the same is true for summer cooling. Access to the ground temperature is quite smart and very efficient. The installation of this system is very costly since you need to dig a trench in order to install the equipment. An air source heat pump has the indoor air handler sitting in your lawn and using the existing heat energy around you. No, it is not as efficient as the other two options, but it is better than a furnace system. Using heat energy rather than creating it saves you money and ensures cleaner air. You are using the outdoor air quality rather than recycling the same, stale air inside. Your indoor air quality has less dust, pet dander and debris in it this way. The expense of a heat pump system, no matter what method is quite expensive. You need either a horizontal or vertical loop system installed in the process and it is not easy. Once the heat pump is installed and operational, you should save enough money for it to pay back itself.