Windmills (& solar) are reliable enough as a frontline energy creator - as long the power grid is connected up over a large enough area, because the wind is blowing somewhere. Add to that other renewables, plus storage mechanisms. Finally, regular power stations (gas / nuclear) as a backup - in this context, I might view gas as clean enough on the basis that we just wouldn't use it that much.
And who knows, maybe someone eventually will discover economically viable nuclear fusion, and we just don't have to worry that much. I seem to recall we recently went through a little spate of excitement on it, although we've been through enough of those over the decades that I'm pretty cynical.