Fictional worked example

Isolate an electricity usage increase

An apartment bill rises after an additional occupant moves in. The statement shows an identical unit price and service fee, so the household checks the billed quantity first.

Open Calculator

Inputs and calculation

Observed bills
Tool inputValue
CurrencyUSD
UtilityElectricity (kWh)
Previous usage180
Current usage240
Previous flat rate (USD/unit)0.25
Current flat rate (USD/unit)0.25
Previous bill (USD)55
Current bill (USD)70

Usage: (240 − 180) × 0.25 = 15. Rate: 240 × (0.25 − 0.25) = 0. Actual bill difference: 70 − 55 = 15. Residual: 15 − (15 + 0) = 0. All effects are in USD.

Tool result · USD 15.00

Same current usage as last period
Tool inputValue
CurrencyUSD
UtilityElectricity (kWh)
Previous usage180
Current usage180
Previous flat rate (USD/unit)0.25
Current flat rate (USD/unit)0.25
Previous bill (USD)55
Current bill (USD)55

Usage: (180 − 180) × 0.25 = 0. Rate: 180 × (0.25 − 0.25) = 0. Actual bill difference: 55 − 55 = 0. Residual: 0 − (0 + 0) = 0. All effects are in USD.

Tool result · USD 0.00

What the comparison shows

The sample bill increase is fully explained by 60 additional kWh. Comparing the two usage readings is more informative here than comparing prices.

Assumptions and limits

Bills establish meter usage for the account. They cannot assign the increase to the new occupant or a particular appliance.

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