[EGreg]

I there is a surplus of electricity at night, then why have batteries? There seems to be no problem at all with just spot market demand in that case!

I thought the issue was that solar panels are generating electricity during the day only. So as someone with solar, you want to sell during the day and buy at night. No?

My point is, rather than using batteries to store huge amounts of energy and lose much of it in the process, find efficiencies and use credits instead.