GREC vs. SREC: What's the Difference and Which Is More Valuable?
A GREC (Geothermal Renewable Energy Credit) and an SREC (Solar Renewable Energy Credit) both represent the environmental attributes of renewable energy, but they originate from very different sources and are calculated on different scales. A GREC is generated by geothermal heat pump systems and is measured in MWh of thermal energy displaced from the grid or fossil fuel sources. In contrast, an SREC is generated by solar photovoltaic panels and is measured in MWh of actual electricity generated. They trade in separate markets with distinct prices, separate legislative mandates, and differing state-specific compliance obligations that homeowners must understand.
The Calculation and Creation Process
SRECs are conceptually straightforward: a solar panel system generates electricity, and for every megawatt-hour (MWh) produced, exactly one SREC is created and logged by a meter. GRECs work differently because they measure thermal energy output, which is not as easily metered by a standard electrical gauge. The calculation for GRECs involves complex formulas that consider system capacity (measured in tons), the system's Coefficient of Performance (COP), the average operating hours for the region, and a specific fuel displacement multiplier. This means that while an SREC represents new green electricity, a GREC primarily represents the Displacement of energy that would have otherwise been used for heating or cooling. Our /how-it-works page goes into deeper detail regarding how these thermal calculations are verified by state regulators to ensure the credits are accurate and tradeable.
Market Volatility and Price Comparison
GREC and SREC prices vary significantly depending on state-level supply and demand as well as the 'Alternative Compliance Payment' (ACP) set by lawmakers. In Maryland, GRECs have shown remarkable stability, trading near $87/MWh in 2025. SREC prices, however, have historically been more volatile, sometimes ranging from $50 to over $150 based on the total number of solar installations and the specific compliance year. The key difference is that GREC markets are newer and generally have a much tighter supply of available credits, which can support more stable pricing near the ACP ceiling for longer periods. SREC markets are more mature and can sometimes suffer from oversupply if solar adoption outpaces the utilities' legal requirements. This makes GRECs a potentially more predictable long-term revenue stream for homeowners who /evaluate their systems as financial investments.
State Availability and Overlapping Programs
The availability of these credits depends entirely on state law. Maryland is currently the primary state where both GREC and SREC markets are highly active and liquid, providing residents with maximum flexibility. Virginia has both programs, but with a different pricing structure that currently favors geothermal slightly in terms of its growth potential. New Hampshire has specialized Thermal RECs but a much smaller and more niche SREC market. Pennsylvania currently has a robust SREC market under its AEPS, but geothermal is classified as Tier II, offering much lower value; however, the proposed PRESS Act would elevate geothermal to Tier I to match solar. If you have both solar panels and a geothermal system on the same property, you are eligible to participate in both markets simultaneously. Check our /states page to see the specific eligibility criteria for your zip code.
Can You Claim Both Credits Simultaneously?
The most frequent question we receive is whether a homeowner can claim both. The answer is a resounding yes. Since GRECs and SRECs come from different mechanical systems and serve different compliance obligations, there is no 'double-dipping' involved. A homeowner with both a geothermal heat pump and rooftop solar can register for and earn both types of credits from the same property. The GREC is derived from the heat pump's displacement of thermal energy, while the SREC comes from the solar panels' electrical production. This dual-credit strategy is the most effective way to maximize your renewable energy revenue and can turn a green home into a significant income-producing asset. To get a combined estimate for your property, you can visit our /calculator and aggregate the potential earnings from both technology types.
Choosing the Right Aggregator for Your Credits
GREC markets benefit from a structural advantage: dedicated 'carve-outs' that create guaranteed demand from utilities. Because there are fewer geothermal systems installed compared to solar arrays, the supply remains low, which often keeps prices trading right at the ACP ceiling. This provides a more predictable revenue floor than many solar markets. However, the complexity of registering a geothermal system—which requires HVAC-specific documentation and thermal calculations—means you need an aggregator who understands heat pumps, not just solar. Emergent Energy specializes in the geothermal niche, ensuring that your GRECs are minted correctly and sold at the highest possible price. Visit our /faq to learn more about our fee structure and how we manage the sale of these specialized certificates alongside traditional renewable credits.
The Impact of Carbon Accounting on Credit Value
One of the reasons GRECs are gaining traction is their role in carbon accounting. As corporations and utilities look to meet 'net-zero' goals, the displacement of fossil fuels for heating (which GRECs represent) is seen as highly valuable compared to just adding more green electricity to an already cleaning grid. This 'additionality' makes GRECs a premium product in the eyes of some environmental buyers. While SRECs are vital for cleaning the power grid, GRECs are the primary tool for decarbonizing the building sector. This fundamental difference in what the credits signify suggests that the GREC market could eventually outpace the SREC market in terms of strategic importance to state regulators. For more information on these trends, our /glossary provides a deep dive into the terminology of carbon offsets and thermal displacement.
Investment Payback: Solar vs. Geothermal
When deciding where to invest in your home, it is important to look at the combined savings and credit revenue. Geothermal systems typically have a higher upfront cost than solar but offer much larger energy savings and higher-value GRECs in states like Maryland. When you factor in the $87/MWh GREC payment alongside the 30% federal tax credit, the 'payback' period for geothermal can be shorter than solar in many Mid-Atlantic jurisdictions. By working with an installer from our /for-installers list, you can ensure your system is optimized for both energy efficiency and credit generation. Ultimately, the choice between GRECs and SRECs doesn't have to be an either/or decision; the two technologies work together to create a fully sustainable, revenue-generating residence.