Time-of-Day Tariff (ToD)

A time-of-day tariff replaces a flat per-unit rate with time-differentiated blocks, typically a discounted solar window during the day, a standard off-peak rate overnight, and a premium evening peak. India's rules require ToD tariffs for commercial and industrial consumers and are extending them to larger residential consumers, with the solar-hours block commonly discounted around 20% and the peak block surcharged by a similar margin. The policy intent is twofold: shift flexible load into the solar surplus window, and create a price signal that makes behind-the-meter storage economic by widening the arbitrage spread between day and evening. For rooftop solar owners the effect is significant, since ToD changes the value of self-consumption relative to export and is often the difference between a battery paying back and not.