The conventional system is a central power plant that distributes electricity from the point of production to the point of consumption. For ideological reasons, these are private sector, for practical reasons they are traditionally monopolies.
A number of years ago, competition of sorts was introduced. The traditional supplier still owns the distribution. However, through customer choice plans, users can choose an electricity supplier.
FWIG, there are a couple ways green energy gets involved. The better way is to install the solar panels and or wind turbines at the point of consumption. Solar for residential and wind for commercial are starting to catch on, kind of.
The other way is via the wind and solar farms, sort of based on the central power plant model. They appear to market green energy via customer choice plans and also subscriptions.
The half baked sort of free market at work. Maybe we ought to socialize public utilities?