Geothermal heat pumps provide heating and cooling using the ground as a heat sink, absorbing excess heat when the aboveground temperatures are warmer, and as a heat source when aboveground temperatures are cooler. While geothermal heat pump systems are typically more expensive than air-source systems, the additional costs are often returned with energy savings.

In 2024, Maryland’s General Assembly enacted the Working for Accessible Renewable Maryland Thermal Heat Act (WARMTH Act) - one of the country’s first networked geothermal pilot programs. The bill requires Maryland’s gas utilities that serve at least 75,000 customers in their distribution territory to develop a plan to pilot a networked geothermal system. Networked geothermal projects are closed loop underground piping infrastructure systems that create a network of customers with thermal energy for heating and cooling through noncombusting electric heat pumps. Under the two-year pilot program, residents in the geothermal loop will be eligible to have electric appliances for heating, cooling, cooking, clothes drying and other water heating installed in their homes. Both BGE​ and Washington Gas have indicated their intent to develop networked geothermal pilots. Pilot project updates filed with the Maryland Public Service Commission can be found under Case No. 9749. Questions about the WARMTH Act may be directed to building.decarbonization@maryland.gov. 

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