As the name implies, ground source heat pumps use the ground as the source for heating and cooling. To select this option in your model, you first need to select the appropriate heating fuel and air-side system. For a GSHP, the fuel (“heating fuel type”) is electricity.
Then, under Air-Side System you’ll see three options with the word “heat pump.” To model GSHP, you’ll need to select “Packaged Heat Pumps.” This will give you two options under Cooling System and Heating System, both of which you can change to Ground Source Heat Pumps.
If you select either of the other two heat pump options, the only cooling and heating system choice will be Air Source Heat Pumps. This is because both of those system types are stand-alone systems which do not utilize an external heating or cooling source: packaged terminal heat pumps are small systems installed at the location where heating and cooling is needed, while packaged single zone heat pumps are larger units often used in place of roof-top units.