Definition
A geothermal heat pump, also called a ground-source heat pump, moves heat between a home and the ground through a buried loop of pipe filled with water or antifreeze solution. Because ground temperature stays far more stable than outdoor air, it gathers winter heat and rejects summer heat more efficiently than an air-source heat pump.
Also called: Ground-source heat pump, Geothermal system, GSHP
Why it matters to you.
Central Kentucky's mix of hot, humid summers and cold snaps means a system works hard in both seasons, and ground temperature stays steady through both. Many rural lots in Boyle, Mercer, Lincoln and Garrard counties have room for a loop field, but parts of Central Kentucky sit on karst limestone, where bedrock depth and sinkholes shape what loop is practical.
Practical guidance.
Consider geothermal if you plan to stay in the home long term, and ask for a site evaluation and load calculation before comparing it with a high-efficiency air-source or dual-fuel heat pump. Loop design, drilling or trenching and refrigerant work are contractor jobs, so ask who handles the loop and who services the indoor unit.
How Geothermal Heat Pump options compare.
| Loop type | How it is installed | Typical fit | Key considerations |
|---|---|---|---|
| Closed loop, horizontal | Pipe laid in trenches several feet below grade | Rural and larger lots with open, diggable land | Needs the most land area; shallow soil over bedrock limits trenching |
| Closed loop, vertical | Pipe inserted in drilled boreholes and grouted | Smaller lots or sites where trenching is impractical | Drilling through limestone and karst features must be planned and grouted properly |
| Closed loop, pond or lake | Coiled pipe sunk in a body of water | Properties with a suitable pond close to the house | Pond must stay deep and large enough year-round |
| Open loop | Well water pumped through the heat pump, then returned to the ground or discharged | Sites with an ample, good-quality well | Depends on well yield, water quality and rules for discharging the water |
How is a geothermal heat pump different from an air-source heat pump?
Both move heat with a refrigerant cycle, but an air-source heat pump trades heat with outdoor air while a geothermal unit trades heat with the ground through a fluid loop. DOE notes ground temperature a few dozen feet down stays relatively constant year-round, so a geothermal system works from steadier conditions in a Kentucky cold snap or July heat, and it has no outdoor condenser.
Which type of ground loop fits a Central Kentucky property?
It depends on land area, soil depth, rock and water. Horizontal loops in trenches need the most open land; vertical loops in drilled boreholes suit smaller lots; pond loops need a suitable pond; open loops need a well with enough good-quality water and a legal discharge. Parts of Central Kentucky sit on karst limestone, so a site evaluation should account for bedrock and sinkholes.
How is geothermal efficiency rated?
Geothermal heat pumps are rated by EER for cooling and COP for heating, not SEER2 and HSPF2, so the numbers are not directly comparable with air-source ratings. ENERGY STAR requires at least 17.1 EER and 3.6 COP for closed-loop water-to-air models and 21.1 EER and 4.1 COP for open-loop water-to-air models. A COP of 3.6 means 3.6 units of heat per unit of electricity.
Can a geothermal system heat my water too?
Many can. A desuperheater option captures surplus heat from the compressor and preheats domestic hot water, usually feeding a conventional water heater tank. It contributes the most during cooling season, when that heat would otherwise go into the ground, and less in winter, when the water heater carries more of the load. Ask whether a proposed model includes one.
About this definition
Written by the Feistritzer Heating & Air Conditioning team — family owned and operated in Danville since 1976, Kentucky HVAC license M02584. Definitions inform; a whole-system diagnosis in your home decides.