In the fight against climate change, renewable energy certificates (RECs) are part of market-based initiatives that gained traction in the early 2000s as a tool for supporting clean energy production. RECs certify that one megawatt-hour (MWh) of electricity was generated from a renewable source and fed into the grid, enabling the REC owner to claim the environmental benefits—the reduced carbon footprint—of that clean energy. When RECs are sold, what's transferred is not the electricity produced by the attributes that make it clean energy, which is separate. It's like selling the right for a utility to take the label "clean energy" and apply it to 1 MWh of power it generated elsewhere. Also known as green tags or renewable energy credits, RECs are meant to provide incentives to support renewable energy production.