Electrons are fungible. They always come out of wires in in my garage, and are mixed on the way from many sources. But since the country wastes THW of night time wind, because they cannot sell it, chances are really good that I'm getting what I'm paying for when I'm paying for it. I bought green electricity before my volt and buy it for all of my power. But I can only buy what I use. I shifted my power from gasoline to renewable electricity.