Know which number you are reading
The unit rate is the price for each kWh used. It is separate from the standing charge, which is usually charged per day, and from payments or balances carried from earlier statements.
Use the rate shown for the relevant tariff
Record the rate, the date or tariff period and whether the meter is single-rate or multi-rate. Do not substitute a headline or current example rate for the rate on your own bill.
The simple cost calculation
For a usage-only sense check, multiply kWh by the rate in pence and divide by 100 to express the usage charge in pounds. Add standing charges separately when the period and daily rate are known.
Use the right tool for the question
Use the electricity cost calculator for usage and rate, the energy bill calculator for a dated period with standing charge, or the Economy 7 calculator when day and night rates both apply.