Units and the slab trap
Your consumption in kilowatt-hours is billed in slabs, and the rate rises as you cross each one. Crossing a slab boundary raises the rate applied to a large part of your usage, so a small increase in consumption can produce a disproportionate jump in the bill.
This is why one hot month with extra air conditioning can look like a metering fault when it is simply slab arithmetic. Compare units consumed month to month before you compare rupees.
Fuel price and quarterly tariff adjustments
The fuel price adjustment passes through the difference between the fuel cost assumed in the tariff and what generation actually cost, usually with a lag of a month or two. It can be positive or negative.
The quarterly tariff adjustment does something similar for capacity payments and other allowed costs. Neither line reflects your own usage pattern, and neither can be disputed at the billing counter — they are set by the regulator.
Taxes and other fees
Expect general sales tax on the energy charge, electricity duty, a television licence fee, and in some cases income tax withholding or a financing surcharge. Meter rent is a fixed monthly line.
For commercial connections, withholding tax depends on filer status, which is one of the few lines you can change by getting your tax filing in order.
When a bill is genuinely wrong
Check the meter reading dates. A billing period longer than about a month inflates units and can push you into a higher slab. Compare the previous and current readings on the bill against the number on your meter today.
If the readings do not reconcile, file a complaint with your supplier's complaint number and keep the reference. A detected meter fault is corrected by re-billing, not by a goodwill discount.