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.
Your details
Enter your details below
Your result
Based on the values you enter
Ofgem GB Direct Debit rate examples: 1 October to 31 December 2026; checked 14 October. Gas includes 5% VAT; electricity has no VAT for this period. Enter your own bill rates; no extra VAT is added. Comparison quotes and usage are illustrative.
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
Use illustrative annual consumption of 2,700 kWh electricity and 11,500 kWh gas, 365 days and no one-off adjustment. The current tariff starts with October–December Ofgem Direct Debit averages:
`2700 × 26.32 / 100 + 365 × 54.83 / 100 + 11500 × 7.97 / 100 + 365 × 29.68 / 100 = £1,935.65` (rounded).
The new-tariff fields are a fictional editable quote: electricity 23.50p/kWh + 65p/day, gas 5.50p/kWh + 35p/day. Their total is £1,632.00, making that example £303.65 cheaper at the entered usage. This is a constant-rate comparison, not a current market offer or the official typical-household price-cap headline. A £50 exit fee reduces the saving to £253.65; a credit increases it.
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.
Default rates and sources
Rate examples were checked on 14 October 2026 against Ofgem unit rates and standing charges for 1 October to 31 December 2026. They are Great Britain averages for Direct Debit, not Northern Ireland rates or a quote for every household. Regional, payment-method, meter and tariff differences matter; use your supplier's applicable rates.
Ofgem states that gas figures include 5% VAT, while electricity has no VAT from 1 October 2026 to 31 March 2027. Enter bill rates with any applicable VAT included: the calculator does not add VAT again. This VAT difference also means costs across the affected periods are not directly comparable. Bills crossing a rate-change date should be calculated separately for each part using its own usage, days and rates.
These examples expire after 31 December 2026; they are not a future tariff forecast. Annualised results assume the entered rates stay constant. Usage amounts and comparison offers are editable illustrations, not current official consumption benchmarks or live supplier offers.
Frequently asked questions
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.
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.