Good stuff! In terms of the 100% renewable I believe my supplier buys the electric wholesale from windfarms and solar only, naturally the actually electric I use comes from all sources that supply the grid.

That being said yeah offpeak times would be any time after 8pm to 9am here in the UK I think. My computer tends to be on throughout the day anyways hense the constant idle crunching but rarely on at night.
I might switch to 24/7 again, I currently run 75% cpu 75% of the time. My computer is also watercooled so it's temps never really get that high but it's really good at heating the room.