Imagine the energy grid as a big pool. The pool is filled by two separate faucets: one is running clean, renewable energy (hydro, wind, solar). The other runs non-renewable energy sources (gas, oil, coal, etc.). The pool is filled with both, the mixture draining every time you use electricity.
A large amount of energy comes from the non-renewable tap, while the rest of the mix comes from renewable sources.
Consumers are the driving force behind the demand for renewable energy. As demand increases, more clean energy infrastructure is built and more clean energy is added to the pool.