This probably depends a lot on how close you are to the equator. Here in Germany output of solar in winter is negligible, and if there is no wind, which can happen for several consecutive weeks, we need a backup. No utilities company will build a fossil power plant that will be used only a few weeks per year, so our government will have to step in to make sure this happens.

On top of this you have very high costs for an increasingly complex grid, which needs to be built and then maintained. Prices will never again be as low as in the fossil/nuclear era.