Lots of gas plants already run only a fraction of the time. This is because demand goes up and down on both a short and long term basis e.g. in many places the peak daily demand is just after lunchtime, and peak yearly demand is mid-summer, with an absolute peak at noon on one summer day. Without grid scale storage demand must be matched, hence ridiculously expensive gas peaker plants and transmission lines built for these peak loads.

It is in fact these very expensive gas plants that solar is destroying the market for first, both because they are the most expensive to run, but also because solar happens to align with the natural peaks in demand.