Additionality

Additionality is a concept used in renewable energy and climate policy to determine whether a specific action (like purchasing RECs or investing in a solar project) leads to new renewable energy generation that would not have happened otherwise. A project has “additionality” if it would not have been built without the specific financial incentive or investment.

This concept is important for understanding the real climate impact of renewable energy purchases. For example, buying RECs from a decades-old wind farm doesn’t create any new clean energy — that farm would have operated regardless. But investing in a new community solar project that wouldn’t exist without subscriber funding does have additionality. For residential solar homeowners, installing panels on your roof has clear additionality — you are directly adding new clean energy generation capacity that would not exist without your investment. The concept becomes more relevant when evaluating corporate “100% renewable” claims, community solar programs, or green energy tariffs from utilities. Programs with genuine additionality have a measurable impact on reducing fossil fuel use, while programs without additionality may just be relabeling existing clean energy.