May was the first month our local electric utility began charging for electricity under a Time-of-Use (TOU) plan. Roughly speaking, we pay 30 cents an hour during the peak hours of 3-7 pm and 20 cents during the remainder of the day and on weekends. When we built the house, I selected a battery backup system to keep it running during a power outage. Incidentally, we had two such events last week. I also wanted a system that could be used to time-shift our energy consumption. It is now programmed to provide electricity for the entire house during peak hours and recharge during off-peak hours. Our bill for May arrived today, confirming that we used zero electricity during peak times. I also programmed our car chargers to avoid peak hours. I estimate the combined savings to be about ~$650 per year.