How to read and compare electricity bills

Start with the period

Confirm the start date, end date and number of billing days. Comparing a 28-day bill with a 35-day bill by total cost alone can create a false trend. If the meter was estimated rather than read, mark that before drawing a conclusion.

• Billing dates and days
• Previous and current meter readings
• Actual or estimated reading status

Find the energy quantity

Electricity is commonly billed in kilowatt-hours, written kWh. One kWh is an amount of energy, not an appliance's power rating. If the bill has peak, shoulder, off-peak or controlled-load rows, keep each kWh quantity with its matching rate.

Separate rates from charges

An energy rate is multiplied by kWh. A standing, supply or customer charge is usually applied per day or per billing period. Taxes, network adjustments, fuel surcharges, demand charges, credits and arrears may follow other rules. Do not combine them until you can explain the purpose of the comparison.

• Use the tariff rate for the next-kWh question.
• Use total bill divided by kWh only as an all-in historical indicator.
• Keep credits and old balances outside a current-use estimate.

Compare two bills in a fixed order

Start with the older bill, extend its daily kWh to the newer bill's number of days, then apply the change in daily usage, the change in effective usage-linked rate and the change in fixed charges. This sequence makes the four effects add back to the exact bill difference. Another order could distribute interaction effects differently, so the order remains visible in the result.

Write down what the calculator cannot know

A calculator sees only the values you enter. It cannot identify a tariff from a logo, decide which bill line is fixed or know whether a government credit will continue. Preserve both bills and the supplier tariff next to the result so another person can reproduce the calculation.