Not at all. Solar thermal with heat storage can be "stand-alone". It actually "mirrors" the demand cycle better than other choices. Cheaper...maybe not. Can also be retrofitted onto existing fossil (or nuclear) plants that use steam generators.
My personal preference is to "go nuclear" all the way, including re-processing and breeder reactors. But solar energy alone CAN run a high-tech civilization.
Not here, not in the winter.