Comment by travisb

That presentation doesn't support your claim. The closest it gets is that solar attached to 4 hours of batteries is, ignoring tax credits, about (it's hard to read accurately from the graph) ~8% more expensive than combined-cycle plants.

But 4 hours isn't near a full night. At least 12 hours of battery storage would be necessary for that, possibly more depending on light angles and the relative supply-versus-demand loading at different times of day.

Roughly from the graph on page 8, that 4 hours of battery costs $22/MWh over solar alone. Presuming no further solar panels were needed, extending that 4 hours to 12 to cover the night would cost around $44/MWh more, bringing the total cost of 24h-reliable solar+battery to around $97/MWh -- WITH tax credits. Without tax credits it would be $20-$30 higher, but the graph is too low resolution to be precise. That compares poorly to the $65/MWh for combined-cycle for one single night -- which gets no tax credits accounted for in that graph.