wind and solar. hydro is environmentally unfriendly but renewable. nuclear is not pratical long term, or in the short term, since it needs to build out an expensive nuclear plant, plus all the regulatory approval you need to get through, can easily take 10 years at the minimum and also there significant resistance to nuclear power plants being built in many states, plus all the need to hire expensive technicins, scientists to maintain a plant. solar, wind is much cheaper and faster to set up. Most govt is are totally resisting to fast track it. because Oil money is in politicians pockets.

our tech is not even close for things like fusion or even geothermal that is in alot of fantasy scifi genre right now.