Economy 7 is not automatically cheaper: enough use must move into the supplier's off-peak window, and standing charges also matter.
The result is not a supplier bill or quote. Unit rates, standing charges, region, payment method, meter type, tariff, VAT, discounts, debt and support schemes can differ. Use values from the same tariff period and bill for a personal check.
Compare Economy 7
Enter rates in pounds per kWh, for example 0.2611 for 26.11p.
The calculation runs in your browser. Values are not sent to the website.
How the calculation works
Single = all kWh × one rate. Economy 7 = day kWh × day rate + night kWh × night rate, plus fixed charges.
Unit-rate energy and daily standing charges are shown separately wherever possible. That prevents a misleading single pence-per-kWh figure.
Worked example in pounds
With 3,500 kWh and 40% at night, 1,400 kWh use the night rate and 2,100 kWh use the day rate.
The example checks the method. It is not a universal tariff or a forecast of your next bill.
What changes the result
The largest differences usually come from:
- off-peak hours
- meter clock
- storage heating
- day-rate premium
- standing charge
How to improve the estimate
Use rates for your region, payment method and meter, including VAT consistently. Match the number of days and do not add standing charges or discounts twice.
Use actual meter readings, separate electricity from gas and compare at least a year for weather-sensitive use. Keep debt repayments and account credit outside consumption cost.
Pre-filled figures are editable, dated reference values with a source.
Frequently asked questions
Will this match my energy bill?
Not necessarily. Regional rates, price changes inside a bill, meter estimates, tariff discounts, debt and rounding can differ.
Does the price cap limit my total bill?
No. It limits rates for covered default tariffs; total cost still rises with energy use.
Sources and review date
Content reviewed on: 2026-08-03.
- Ofgem – switch energy supplier — tariff comparison