Merely being cheaper won’t do it. As long as more expensive sources are useful, and as long as solar is supply constrained, no reason that solar growth would cut into carbon usage.

Sure, and where does most of that energy come from today, and how do you propose we replace it? Because that's the whole point, isn't it?

> can use any convenient energy source

Sure. Right now it's mostly fossil though, and it's not like photovoltaic is even close to changing that. Of course if you assume a theoretical clean energy to build your photovoltaic, then that's clean (in terms of CO2), but if you have that clean source, why do you need photovoltaic in the first place?

I think that's a real problem that gets ignored too often: fossil fuels are limited, and we seem to be around peak production right now. So fossil fuel will go down, that's pretty sure. The question is whether we will be able to compensate, and it's really not a given.