Electricity unit calculation: meter readings and appliance kWh

IESCOBillDesk · Reviewed 28 October 2026

Calculate a basic meter-reading difference

Suppose the previous reading is 12,450 and the current reading is 12,610. Subtracting 12,450 from 12,610 gives 160 units. These are invented values for an example. Use the same register and the dates shown on the bill. If the meter was changed, a multiplier applies or an adjustment appears, ask the supplier how the recorded units were derived.

Estimate consumption for one appliance

A 100-watt appliance running for five hours uses an estimated 0.5 kWh: 100 divided by 1,000, multiplied by five. If it runs for that duration on 30 days, the simple estimate is 15 units. Actual consumption depends on the real power draw and operating time. A label may show a rated maximum rather than constant use.

Why refrigerators and air conditioners need care

Appliances that cycle on and off do not necessarily draw their rated power continuously. Temperature settings, room conditions, equipment condition and usage patterns can affect consumption. A calculation using maximum watts for every hour may overstate normal use, while an optimistic running-time assumption may understate it. Treat appliance arithmetic as a planning estimate and compare it with measured usage.

Keep peak and off-peak registers separate

If the account uses separate time-of-use registers, record each field under its own label. Do not subtract an off-peak value from a peak value or merge the readings before understanding the bill. Confirm which figures represent cumulative readings and which represent consumption for the period. The tariff schedule determines how the applicable consumption is charged.

Compare similar periods rather than totals alone

Write down the number of days between readings and any major change in appliance use. A longer billing interval can increase units even when daily habits look similar. Compare with a similar season where possible. Keep the current and previous bill together so you can review units, period and category without confusing the figures.

Turn units into a bill review, not a promised price

The final amount can include category-dependent energy charges, fixed charges, taxes, earlier balances and adjustments. Multiplying every unit by a single headline rate can miss these components. Use the unit calculation to understand consumption, then review the actual bill lines. If the readings or units look inconsistent, note the specific discrepancy and ask the supplier for an explanation.

Frequently asked questions