Large users like the supermarkets have agreements with electricity providers that they will reduce their use at certain times in return for a discount. Tesco d

Large users like the supermarkets have agreements with electricity providers that they will reduce their use at certain times in return for a discount. Tesco doesn't care if the freezers in store run at 04:00-04:15, or 04:30-04:45, and will pick whichever is cheaper.