- GREC (Geothermal Renewable Energy Credit)
- A tradeable certificate representing 1 MWh of thermal energy produced by a geothermal heat pump system. GRECs are issued by PJM-GATS or NEPOOL-GIS and sold to utilities to fulfill Renewable Portfolio Standard obligations.
- SREC (Solar Renewable Energy Credit)
- A tradeable certificate representing 1 MWh of electricity generated by a solar PV system. SRECs are distinct from GRECs, which represent thermal energy rather than electrical generation.
- T-REC (Thermal Renewable Energy Credit)
- The credit unit used in New Hampshire and some other ISO-NE states. One T-REC equals 3,412,000 BTUs (1 MWh equivalent) of useful thermal energy output. New Hampshire T-RECs are tracked via NEPOOL-GIS.
- RPS (Renewable Portfolio Standard)
- A state regulation requiring electric utilities to procure a minimum percentage of their power (or equivalent credits) from renewable sources. RPS obligations create the compliance demand that gives GRECs their value.
- Carve-out
- A provision within an RPS that requires utilities to source a specific percentage of credits from a designated technology. Maryland and Virginia have dedicated GREC carve-outs, ensuring demand specifically for geothermal credits rather than allowing substitution with other renewable technologies.
- ACP (Alternative Compliance Payment)
- The maximum price a utility will pay per credit before it becomes cheaper to pay the state's ACP penalty instead. The ACP functions as a ceiling on GREC market prices. Maryland's ACP declines from $100 to $65 over the program life; Virginia's ACP ceiling is $45/MWh.
- PJM-GATS (PJM Generation Attribute Tracking System)
- The tracking system for renewable energy credits in the PJM interconnection territory, covering Maryland, Virginia, Pennsylvania, Delaware, New Jersey, Washington DC, and parts of the Midwest. PJM-GATS issues, tracks, and retires GRECs for systems in those states.
- NEPOOL-GIS (New England Power Pool Generation Information System)
- The REC tracking system for ISO-New England states, including New Hampshire, Massachusetts, Connecticut, Rhode Island, Vermont, and Maine. New Hampshire T-RECs are tracked via NEPOOL-GIS rather than PJM-GATS.
- Tier 1 / Tier 2
- Credit classification levels used in many state RPS frameworks. Tier 1 credits represent newer, preferred renewable technologies and command higher prices. Maryland and Virginia GRECs qualify as Tier 1. Pennsylvania's PRESS Act (HB 501) proposes moving geothermal from Tier 2 to Tier 1.
- Vintage
- The compliance year in which a GREC was generated. Vintage matters because some state RPS rules limit how old a credit can be and still be used for compliance. Earlier vintage credits from the same system may have fewer remaining eligible years.
- Aggregator
- A company that pools GRECs from many individual system owners and sells the aggregated portfolio to utilities. Aggregation allows small residential systems to participate in wholesale GREC markets that would otherwise be inaccessible.
- Manual J
- A heating and cooling load calculation standard (ACCA Manual J) that determines the precise heating and cooling capacity needed for a building. Some states (including Maryland) require a Manual J calculation as part of GREC registration documentation.
- COP (Coefficient of Performance)
- A measure of heat pump efficiency: the ratio of thermal energy output to electrical energy input. A higher COP means more GRECs per year for the same system size. Used in GREC generation calculations.
- ENERGY STAR
- A U.S. EPA program certifying energy-efficient products. Maryland requires residential geothermal systems to meet ENERGY STAR standards for GREC eligibility.
