I think least electricity is used between probably 7-8a.m. and 4-5p.m.
This is because, around those times, the suns already out. Depending on how sunny it is, it may not be as cold as all the other times of the day. And by then, buildings are typically already warmed all up. Everybody's body heat also may play a factor in buildings. ( if there is a ton of people )
