Ann: Mungari Solar Farm, page-54

Agreed, its all about stability. Battery backup only gives some stability on the short term unless its a huge facility, diesel or similar will always be required as a redundancy and for overnight operations.

A figure I've heard bandied about is that for each minute a plant is not in operation the company takes a hit of $10,000 worth of income. I don't think that's even close to being accurate but it shows that power stability is a huge thing.