[DennisP]

If we have to build twice as many widget factories to make up for shutting them down at night, that's another cost to society that we should take into account. I've seen a lot of renewables advocates talk about "demand management" but not any estimate of this cost.

There's also heating, air conditioning, street lights, etc. Aluminum plants, which can't shut down more than 4-5 hours without major damage from the metal solidifying.

Before long, electric vehicles charging in people's garages at night; it'd be nice if we used them to supply the grid at night but that would require parking lots full of charging stations where everybody works, plus new infrastructure in people's houses, and some kind of incentive to get people to bother. All that costs money too.