Going 100% solar makes little sense.<p>Something like power generation capacity, of peak load, for 
30% solar, 30% wind, 30% natural gas, 30% hydro, 30% nuclear and 30% compressed air storage. Note it goes over 100% so that parts of it can be offline and peak demand can be still supplied.<p>The only fossil fuel, natural gas, would only be fired when electricity price was very high, like it is operated in many places already today. It is suitable for this use as the investment cost is low and the reaction time is short.