The short answer

Compare energy in kWh over the same billing period before comparing money. A bill can cover loads missing from your list, while appliance labels and short samples may not describe those exact days. Fixed charges affect the amount paid without adding kWh. A remaining difference is unexplained energy, not proof of a faulty meter or overcharging.

Use the check a bill period calculator
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Compare kWh first, then money

An appliance estimate covers the equipment and assumptions entered. An electricity bill covers the meter’s billed consumption and its tariff rules. Those boundaries are often different.

Start with the billed electricity kWh and the matching period, not the payment amount. The US EIA distinguishes power in watts from energy over time in kWh and explains utility metering. Ofgem separately explains the unit rate, daily standing charge and account-credit effects on a Great Britain bill. Neither a payment nor an account balance is an appliance’s energy use.

The bill-period appliance check compares your estimated appliance kWh with the billed kWh you enter. It works from your inputs and cannot read your supplier account, test the meter or decide that a bill is wrong.

Match the dates and consumption basis

Use the number of days covered by the actual statement or meter-reading interval. A 31-day bill is not the same period as a four-week routine, and a monthly payment can be intended to smooth spending across seasons.

Check whether the statement is based on actual or estimated readings and whether it includes a correction for another period. Keep import, export and generation figures separate if present. Use the supplier’s explanation of each register rather than assuming every displayed kWh quantity has the same meaning.

For each appliance, choose evidence that fits those days:

Available evidence Billing-period treatment
Measured kWh across the exact interval Use once, if the boundary matches the appliance or group
Representative complete-day sample State the daily average and projected use days
Per-cycle figure Multiply by the number of comparable completed cycles in that period
Power and time Use the average power and actual hours, with the constant-power assumption visible
Annual label quantity A prorated average can be an assumption; it is not measured consumption for a particular month

Do not divide a heater’s seasonal use across 12 equal months and then treat that as a cold month’s measurement. The same problem can apply to cooling and moisture-control routines. The household planner is useful for annual patterns; a billing-period check needs its own matching period.

A worked gap without a diagnosis

Suppose an illustrative statement covers 400 kWh across 30 days. Your non-overlapping appliance estimates for those exact days are:

Defined estimate Period energy
Fridge 30 kWh
Electric heater 90 kWh
Complete cooking tasks 20 kWh
Television and home-network group 40 kWh
Laundry tasks 10 kWh
Sum of estimates 190 kWh

The difference is 400 − 190 = 210 kWh, or 52.5% of the entered billed energy. This is the part not explained by those estimates. It is not 210 kWh of proven waste, a saving opportunity or evidence that the supplier overcharged.

Edit the illustrative bill-period example and replace the illustration with your own billed kWh, period and device figures. If estimates exceed billed consumption, keep the negative difference visible and inspect dates, duplicated loads and source assumptions; do not force the result to zero.

Check missing loads before blaming one appliance

Your list may omit lighting, cooking components, hot-water equipment, space conditioning, extra refrigeration, pumps, charging or powered electronics. Only include equipment actually present. A small always-on load can accumulate energy across many hours; the standby audit helps inventory those devices.

Prioritize large and uncertain entries. For example, refine the use time and thermostat behavior of an electric heater, the observed operating routine of a dehumidifier or the complete-meal boundary of a cooking comparison. These checks are more useful than assigning every missing kWh to whichever device was measured last.

Remove overlaps before adding more precision

A measured entertainment power strip already includes the connected TV and console. A complete cooking measurement already includes captured preheating. A full-day washer socket sample may include waiting energy between cycles. Do not add those same components again as separate rows.

Likewise, a whole-home meter reading cannot serve as one appliance’s measurement and then be added to other devices. The measurement guide explains how to retain a clear boundary in the journal.

Money can differ even when energy matches

For an illustrative flat-rate bill of 400 kWh at £0.28/kWh plus £0.50/day for 30 days, energy costs £112 and fixed charges cost £15, totaling £127 before any other items. Dividing £127 by 400 gives £0.3175/kWh, but avoiding one extra kWh would save the entered £0.28 variable charge, assuming that rate applies.

US supply and delivery components can appear separately. Great Britain bills can include a standing charge. Northern Ireland and EU tariffs have their own component and tax arrangements. Use the units and applicable terms on your own bill; the tools do not add taxes or reproduce every tier automatically. With time-of-use or tiered pricing, equal kWh can still have different costs depending on when or in which band they were charged.

Solar generation, exports and battery charging or discharge can make grid-import kWh differ from total appliance use. A simple billed-import comparison cannot resolve those flows without compatible records. Identify that boundary before interpreting a gap.

Choose one useful next check

First confirm the period and billed reading. Next remove duplicated energy and identify missing equipment. Then repeat a representative sample for the largest uncertain item, retaining the programme, weather and routine. Compare saved observations on the same basis rather than presenting a settings change as a controlled experiment.

If the statement or readings still appear inconsistent, ask the supplier to explain the specific period, register and charges. A calculator result can help organize the question; it cannot establish meter accuracy or a billing fault.