Where is this month’s bill heading?

It divides the units you have used so far by the days since your last reading, and multiplies by the days in your billing cycle. Then it runs that projection through your state’s tariff, the same way the bill calculator does.

Every bill prints a “present reading” or “current reading”. That is the starting point for this cycle. Today’s reading is on the meter display; on most digital meters it is the kWh figure.

A point where one extra unit adds a lump sum to the bill, not just that unit’s price. It happens where a state re-rates every unit once you cross a line (Kerala above 250 units a month, Tamil Nadu above 500 in two months) or where the fixed charge steps up with use. The tracker tells you how many units a day keep you under it.