What it means to “buy renewable energy”
Unless you have a renewable energy system, such as solar panels, plugged directly into your home or office, you cannot purchase the specific electricity that is generated by a renewable energy project. The electricity flowing through the grid is a mix, and it includes electricity generated by renewable energy projects as well as electricity generated by fossil fuels, such as coal, oil, and gas, and other resources, such as nuclear. The individual sources cannot be separated out at the level of the grid.
As a result, a separate system has been created to keep track of renewable energy and to allow it to be bought and sold. That system uses renewable energy certificates, or RECs. Every time a renewable energy project generates 1 megawatt-hour of electricity, 1 REC is minted. That REC can then be sold. Purchasing a REC gives you the right to say you used the electricity from that renewable energy project.
Anyone who wishes to purchase renewable electricity must then purchase 2 things: they must purchase the electricity itself from the grid, and then they must also purchase RECs for a percentage of electricity usage that they want to claim as green. (These two costs are often bundled together, and they are why renewable energy costs a bit more.) Those RECs are then retired so that they cannot be purchased by anyone else, and no one else can claim to have used that renewable electricity.
The Green Worcester ElectriCITY Municipal Aggregation Program is purchasing RECs in order to integrate an increased amount of renewable energy into the City’s electricity supply. No one else will be able to claim the energy associated with the RECs that Worcester buys.