Some utilities are forced to either curtail or sell solar power at low load times (winter or spring mornings). You are required to run a certain amount of conventional generation sources at all time, because you can't control solar and wind generation. Large solar facilities will be producing their maximum output at 10am, when load doesn't peak until 6 or 7pm in the winter. Storage technology has not caught up, so the only solution is to sell it or turn it off.

The way that many of the contracts with the solar facility operators work, is that you pay them if they could make energy and you force them off. Sometimes the most cost effective solution is to pay someone to take your energy, as the entire west coast is in the same situation of over-production at the same time. In California, there are mandates to meet for green energy, so you might have to give away or pay for a utility in AZ or UT to take your gas/coal generation for the hours of over-production. You are effectively shifting the burden to a state that has less green energy.

All of this has entirely nothing to do with meeting peak summer demand.