Ground Source Heat Pumps: Geothermal Explained Ground source heat pumps are heating and cooling systems that move heat between a building and the ground using a buried loop of pipe and a refrigerant-driven heat pump. For DIY eco homes, a properly designed ground source heat pump can cut winter heating bills by two-thirds compared with resistive electric heating and deliver steady performance in cold weather. This article explains what a ground source heat pump is, how the ground loop and heat pump work together, the main system options (horizontal trench vs vertical bore), planning and budget considerations for self-builders, and routine maintenance you can handle yourself. TL;DR: - Ground source heat pumps typically deliver a seasonal COP of about 3–5, saving roughly 40–70% on heating energy versus gas or electric resistance. - Choose horizontal loops for low-cost land-rich sites and vertical boreholes for small lots; expect installed costs commonly in the $15,000–$40,000 range depend...