[milicat]

Well, it makes a difference what kind of energy supplier turns a profit from your energy consumption. If you're buying renewable energy from a company that still invests into fossil fuels, it's fairly useless. If you buy it from a company that mainly builds up renewable energy production capacity, that helps the transition.

Of course, even a 100% renewable supplier needs to buy from the market to smooth out peaks in energy consumption for their customer base.

(disclaimer: i work for such a renewable energy supplier)