Usually, the energy company is already producing both energy by both renewable and non-renewable means. You can pay them to say that your energy is only coming out of the renewable side. This does not really affect anything in the actual energy production, it is just bookkeeping. It's still fed into the same power grid. The only real way it affects the energy production is if the demand for renewable gets high enough that it exceeds the actual renewable production.
I wondered if something special happened when a big company like Apple bought 100% wind energy. They could be paying above market price as you could do at some point if you were a simple private consumer. But more likely they are paying less.