Comment by sephamorr

This is a relatively good point. In the California electricity market, the increase in renewables results in a very large power-ramp rate in the late afternoon (nothing unique to California). In general, more-efficient power plants either cannot, or lose efficiency, when changing operating power levels. A ~60% efficient combined-cycle gas plant cannot ramp power very much, which results in the grid building and running more ~40% efficient gas turbines, which can ramp their power output in order to meet the early-evening power ramp. Interestingly, at this point, adding more Solar to the California grid results in very little emissions reduction, since the additional solar displaces efficient baseload generation with inefficient ramp-able load. The solution, of course, is storage.