My suspicion is that if you luck back to the 1980s, before all the natgas fired plants got built, that the summer trough as a % of the winter peak was much lower.  The fact that so many peaking plants are natgas fired only exarcerbates this. Peak electric demand comes with AC in the summers, which means that natgas that could be stockpiled for the winter, reducing home heating prices, is burned in the summer. Dirty game here.

And I'll give my consent to any government that does not deny a man a living wage-Billy Bragg