While in some parts of the world, you can buy power from a company that only sells renewable power, there are other parts of the world where the grid is regulated to the point that you don’t even have choice of supplier – if they burn coal, and you need to run a server in that part of the world, there’s no other option. Elsewhere, there may be places where company A sells renewable power, but also sells the fact that energy has been generated with renewable power separately, so that another company B, can buy this credit, and then say they use green power, even if the supplier they use is relying on fossil fuels to generate electricity for their servers .