Suppose Provider A is 100% renewable and Provider B is 100% fossil. Both providers generate power and feed the same grid (which is managed separately from the various energy providers). The same grid powers all homes. Householders get to choose whether to buy from Provider A or Provider B. If you support renewables then you buy from Provider A; their share goes up and B’s share goes down. And vice versa for B. In addition the government juggles A,B as well as C,D,E,etc to provide the overall service to the country.
Suppose Provider A is 100% renewable and Provider B is 100% fossil. Both providers generate power and feed the same grid (which is managed separately from the various energy providers). The same grid powers all homes. Householders get to choose whether to buy from Provider A or Provider B. If you support renewables then you buy from Provider A; their share goes up and B’s share goes down. And vice versa for B. In addition the government juggles A,B as well as C,D,E,etc to provide the overall service to the country.