Residential Hydro Electric?

Just wondering if this exists? Since I live on a river I was brainstorming on how I could use it to generate power for the house. The river flows into a pond into my backyard then through a dam, so I know there is enough flow to move a turbine but I don't have any idea if this is legal and how much it would cost? It would be great to call up northeast utilities to have them come remove the meter from my house since I don't need it anymore!