Geothermal HVAC: Ground-Source Heat Pump Guide

Quick answer: Geothermal HVAC uses a ground-source heat pump to transfer heat between a building and the ground or groundwater through a loop or collector. It can heat and cool, but final equipment and loop decisions require a building load and a site review.

What geothermal HVAC includes

A geothermal HVAC system has three connected parts:

Heat pump: moves heat between the building-side distribution system and the ground-side heat-transfer circuit.
Ground loop or collector: exchanges heat with soil, rock, or groundwater. The loop may be arranged horizontally, vertically, or in another site-specific configuration.
Distribution system: delivers heating or cooling to rooms through ducts, hydronic piping, or another compatible system.

The U.S. Department of Energy describes these as the heat pump, ground heat exchanger, and distribution subsystem. The installation site determines which loop arrangement and distribution method can work.

How geothermal heating works

In heating mode, the ground-side circuit collects heat and the heat pump raises its temperature so the building can use it. The ground temperature is generally steadier than outdoor air, but the useful capacity still depends on the equipment, loop, building load, and local conditions.

In cooling mode, the cycle reverses: the heat pump removes heat from the building and rejects it to the ground or groundwater. That is why one geothermal heat pump can provide both heating and cooling.

Closed-loop and open-loop systems

Arrangement	Heat-transfer medium	What must be reviewed
Closed loop	Fluid circulates through buried or submerged piping.	Available land or drilling access, soil and rock conditions, loop design, and water-quality protection.
Open loop	Groundwater is used directly as the heat-transfer medium.	Water availability and quality, well performance, discharge or return requirements, and local permitting.

These labels describe the heat-transfer circuit; they do not by themselves determine cost, capacity, or suitability. A qualified designer must check the site and local requirements.

Geothermal versus air-source heat pumps

Both systems use a heat pump to move heat and can provide heating and cooling. The key difference is the heat source: an air-source system exchanges heat with outdoor air, while a geothermal system exchanges heat with the ground or groundwater. The ground-side circuit adds a site-design step, so a geothermal project needs more than an equipment size selected from floor area.

What to calculate before choosing equipment

Start with the building rather than the loop. A preliminary review should document:

room and envelope areas, insulation, windows, and doors;
air leakage or infiltration assumptions;
indoor setpoints and the local heating and cooling design conditions;
existing ducts or hydronic distribution and their condition; and
the required heating and cooling capacity at the design conditions.

Use the heating load calculator for a preliminary load model, then compare the result with the heat pump sizing calculator. These tools are a sizing handoff, not a geothermal loop design or a substitute for a site-specific engineering review.

What this guide does not determine

This page does not provide an installed price, payback period, tax-credit or rebate eligibility, drilling quantity, loop length, permit decision, or final equipment selection. Those answers depend on current jurisdictional rules, site data, equipment ratings, and a professional design. Treat any such number as unverified until it has a dated source and a project-specific review.

Frequently asked questions

What is geothermal HVAC?

Geothermal HVAC uses a ground-source heat pump to transfer heat between a building and the ground or groundwater through a loop or collector. The heat pump and the building's distribution system move that heat indoors or outdoors as conditions change.

Does geothermal HVAC provide cooling?

Yes. A geothermal heat pump can reverse its heat-transfer cycle so it removes heat from the building and rejects it to the ground or groundwater. The distribution system still needs to be sized and configured for the building.

What is the difference between closed-loop and open-loop geothermal systems?

A closed-loop system circulates a heat-transfer fluid through buried or submerged piping. An open-loop system uses groundwater as the heat-transfer medium and returns or discharges it under applicable local requirements. Site conditions determine which arrangement is practical.

Can I size a geothermal system from square footage?

Square footage alone cannot determine final geothermal equipment or loop design. Start with a building heating and cooling load using measured envelope, air-infiltration, and design-condition inputs, then have the loop and equipment reviewed for the site.

Sources reviewed 2026-10-04

Disclaimer: This guide is for education and preliminary planning. Verify final equipment, loop, water, code, and permit decisions with qualified local professionals.