School districts across the nation are starting to replace conventional electric Heating, ventilating, and air-conditioning systems (HVACs) with ground source heat pumps (GSHP). Since the 1990s, when a handful of campuses installed the first GSHP systems, the technology has proven reliable and efficient with energy costs 30 to 50% less than the chiller systems of old. Many new schools now forgo the old roof-top units to install GSHPs connected to 250-foot-deep wells that transfer heat via water-filled polyethylene tubing.