Bill comparison · Home energy
A higher bill is rarely explained by one number. Compare two bills and separate what changed in consumption, billing-period length, the reported total and the average cost per kWh — then see what the figures support and what they do not.
Copy the figures from the bills you want to compare. Billing dates, kWh used and the reported total are required; itemised charges are optional and are never assumed to be zero.
Enter both bills and press Compare My Bills. You will get the usage and bill changes, like-for-like daily figures, average cost per kWh, itemised differences and a list of what to check next.
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A bill comparison shows that consumption changed, not which appliance caused it. These monitors add the measurement — choose how far you want to investigate.
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Compatibility, installation requirements and price can change. Confirm the exact model and current details on the Amazon listing before buying. These monitors measure electricity use; they do not diagnose a meter fault or a billing error.
The comparison moves from dates, to like-for-like usage, to price. Each step can explain part of a change, and none of them on its own proves a fault.
The checker counts billing days inclusively and warns when the two periods overlap. A 31-day bill against a 28-day bill can rise without any change in daily habits.
Raw kWh and daily kWh are both reported. When period lengths differ, the usage diagnosis uses kWh per day so extra days are not mistaken for extra consumption.
Reported total divided by kWh gives the average cost per kWh. If usage was flat while that figure rose, the next place to look is rates, fixed charges, taxes, adjustments or arrears.
Two bills, both covering 30 days in USD: 300 kWh and a 9,000 total, then 390 kWh and a 12,500 total. The extra days do not explain anything here because the periods are the same length.
Usage rose 30.0%, but the bill rose 38.9%. Because the bill grew faster than the energy used, average cost per kWh also increased. That points to a price or charge effect on top of the extra consumption — it does not, by itself, show what caused either change.
Press Load example bills in the calculator, then Compare My Bills, to reproduce every figure below.
| Measure | Previous bill | Current bill | Change |
|---|---|---|---|
| Billing period | May 1 – May 30, 2026 | Jun 1 – Jun 30, 2026 | 0 days |
| Electricity used | 300 kWh | 390 kWh | +90 kWh (+30.0%) |
| Daily usage | 10 kWh/day | 13 kWh/day | +3 kWh/day (+30.0%) |
| Reported total | $9,000.00 | $12,500.00 | +$3,500.00 (+38.9%) |
| Average cost per kWh | $30.00 | $32.05 | +$2.05 (+6.8%) |
| Unit rate | Not supplied | Not supplied | Not compared |
Billing days = end date − start date + 1 (inclusive)
Daily usage = kWh used ÷ billing days
Usage change % = (current kWh − previous kWh) ÷ previous kWh × 100
Bill change % = (current total − previous total) ÷ previous total × 100
Average cost per kWh = reported total ÷ kWh used
In the example, 390 − 300 = 90 kWh, and 90 ÷ 300 × 100 = 30.0%. The reported total moved 12,500 − 9,000 = 3,500, and 3,500 ÷ 9,000 × 100 = 38.9%. Average cost went from 9,000 ÷ 300 = 30.00 to 12,500 ÷ 390 = 32.05.
This is a comparison of the figures you enter, not an audit of your supplier's records or your meter. Two bills are two observations, not a trend. Weather, occupancy, new appliances, estimated readings, billing dates and tariff changes can all move a bill between periods.
A higher bill does not, by itself, establish a meter fault, a billing error, fraud or theft. Only your supplier or an independent meter test can determine a meter accuracy issue. For an official determination, contact your supplier and, where appropriate, your energy regulator.
Itemised charges are compared as reported and are never added to the reported total again. Blank fields are treated as not supplied, not as zero. A blank optional charge therefore produces “not compared” rather than an invented change.
Need to estimate a bill from meter readings instead? Open the Electricity Bill Calculator. To see what is using the energy, start with the Home Electricity Usage Calculator or the Appliance Power Consumption Calculator.
A bill can rise from a higher unit rate, changed fixed charges, taxes or surcharges, adjustments, arrears, a longer billing period or estimated readings. This checker separates usage from average cost per kWh so you can see which direction each signal moved. It cannot confirm which charge your supplier applied; compare the itemised lines and ask your supplier for a breakdown.
Divide kWh used by the number of billing days, counting both the start and end dates, to get daily usage. Compare kWh per day rather than raw kWh, and also compare cost per day if you want a like-for-like spending view. The checker calculates daily usage automatically and uses it for the usage diagnosis when the two periods differ in length.
Average cost per kWh is the reported bill total divided by the kWh used, so it reflects fixed charges, taxes, adjustments, arrears and other items included in that total. A unit rate is the price per kWh for energy if your bill states one. The two can move differently, which is why the checker reports both separately instead of treating one as the other.
No. Two bills cannot establish a meter fault, a billing error, fraud or theft. Weather, occupancy, new appliances, estimated readings, billing dates and tariff changes can all raise a bill. For an official determination, contact your supplier and, where appropriate, your energy regulator. If a meter accuracy problem is suspected, ask your supplier about its meter-testing and complaints process.
A blank field means the charge was not supplied; zero means the bill reports a zero amount. Treating a blank as zero could invent a change that never appeared on the bills. The checker only compares an itemised charge when a value is supplied for both periods, and it labels the line as not compared otherwise.
The checker applies one selected currency to both bills and does not perform exchange-rate conversion. Compare bills issued in the same currency, or convert one bill to the other currency first using a rate you trust. Mixing currencies in one comparison would make the reported changes meaningless.
The diagnostics treat a change of 5% or more in usage, daily usage, the reported total or average cost per kWh as material, and they use daily usage when the billing periods have different lengths. That 5% threshold is a reading aid defined by this tool, not an official standard or a conclusion about your bill.
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