Bills & Utilities
UK Energy Tariff Comparison Calculator
Compare current and new tariff costs for electricity and optional gas, including the standing charge tradeoff that headline unit rates can hide.
Inputs
Results
Useful next checks
- Check the inputs before relying on the result.
- Try a second scenario to compare outcomes.
- Read the guide below for context.
# UK Energy Tariff Comparison Calculator
Compare two UK energy tariffs using your own annual or bill-period usage, unit rates, standing charges, and any one-off switching cost or credit.
What this calculator does
This calculator compares the full cost of a current tariff and a possible new tariff. It includes standing charges as well as unit rates, because a lower unit rate can be outweighed by a higher daily charge, and the reverse can also happen.
How it works
For each fuel and tariff:
`usage in kWh x unit rate in pence / 100 + standing charge in pence x days / 100`
The new tariff can also include a one-off adjustment. Enter an exit fee as a positive number, or a credit as a negative number.
Example calculation
If a new tariff saves GBP 5 on unit rates over a month but adds GBP 8 in standing charges, it is GBP 3 more expensive for that usage level before any exit fee or credit.
How to use the result
Use the result to compare fixed, standard variable, dual-fuel, and single-fuel tariff offers using the numbers suppliers provide. Compare total cost, not just the headline p/kWh rate.
Assumptions and limitations
This calculator does not check supplier availability, exit rules, smart-meter requirements, payment method eligibility, debt, warm home discounts, or regulated switching protections. It is a bill arithmetic tool only.
FAQs
Why include standing charges?
Standing charges are part of the tariff and are paid daily. They can materially change whether a tariff is cheaper for low, medium, or high users.
Can I compare electricity only?
Yes. Choose electricity only and leave gas out of the comparison.
What should I enter for days?
Use 365 for an annual comparison, or use the exact number of days in a bill period if you are checking a statement.
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Frequently asked questions
Why can a lower unit rate cost more overall?
A higher standing charge or one-off fee can outweigh a lower p/kWh rate, especially for low usage.
Can this replace a switching comparison site?
No. It compares arithmetic from rates you enter, but it does not check eligibility, market availability, or supplier rules.