A renewable energy certificate, or REC, is a certificate proving that a set amount of electricity was generated from a renewable source such as wind, solar, or hydropower. It carries the clean quality of that power and can be sold on its own.
Electricity from a wind farm and electricity from a coal plant become the same current once they mix on the grid, so no buyer can trace the exact clean electrons to their outlet. A REC fixes that by recording the clean quality separately. For each set amount of renewable power put onto the grid, one certificate is issued that stands for that clean generation.
Because the certificate is separate from the power, it can be sold on its own. A business that wants to back its electricity use with renewable power buys RECs equal to what it uses, even though the actual electrons running its lights came from the general grid. The certificate is the proof and the claim.
This is the same idea as book-and-claim accounting applied to electricity. The clean attribute is booked when the renewable power is made and claimed when a buyer purchases the certificate, with each certificate honored only once so the same clean power is never counted twice.
For a fuel marketer, RECs matter where electricity enters the fuel story, such as charging electric vehicles or powering the production of a clean fuel. Renewable power used in those places can be backed by RECs, and that clean electricity can lower the carbon intensity score of the fuel or the charging it supports.
In useA company keeps drawing ordinary power from the grid but buys renewable energy certificates to match its usage, so it can show its electricity is backed by clean generation.
See also Environmental attribute, Book-and-claim accounting, Hydrogen