> There's an energy mix for a variety of reasons.
Exactly. One big reason is that some of the stable, reliable sources aren't as clean as we'd like (coal, natural gas, nuclear), while the clean sources are either not as reliable (wind, solar) or available only in very limited locations and amounts (hydro, geothermal).
The mix allows us to use the cleanest stuff when and where it's available, then throttle the slightly less-clean stuff like natural gas to meet demand, with something very steady like nuclear providing a base level that meets minimum demand.
If you're interested in the mix, here's a paper that may interest you. Of course all figures in the paper are cited to reliable sources. It seems like _maybe_ you don't care for math at all, and if that's the case this paper isn't for you. If you don't mind just a little math, this paper goes over many different sources in the mix, discussing the costs and benefits of each, and how they can be combined.
The figures for solar-electric have improved a bit in the last 2-5 years, so the solar-electric number in the paper are very slightly outdated. The conclusion hasn't changed though - solar electric is a good supplemental source, not a reliable inexpensive source capable of providing the bulk of of energy needs.
The paper, if you're interested and don't mind some fairly easy math: