Grizz, the guy I drink coffee with while we create schemes to power the world, has this dream of living next to a stream where he can place a water wheel to power his house.
But (common theme here) we live in a drought-stricken desert. So, the stream-power scheme is only a dream.
Today, though, I saw this article about an old device that generates electrical power by utilizing the power of water flow.
So, why could this idea not be adapted to modern plumbing? Place it before your shower head, or the dishwasher, or the water heater, or...
May your head be swimming with ideas!