Fixed vs Variable Energy Tariff Calculator UK
This fixed vs variable energy tariff calculator helps you compare two common tariff options using your expected electricity and gas usage. It is designed for UK households that want a practical estimate of which option may cost less over a chosen period.
You can use it to compare a fixed tariff against a variable tariff by entering unit rates, standing charges, exit fees and your own assumption for how variable prices may change.
What this calculator includes
- Electricity and gas usage inputs
- Fixed tariff unit rates and standing charges
- Variable tariff unit rates and standing charges
- Expected percentage changes for variable prices
- Exit fee impact for the fixed tariff
- Total cost comparison over your chosen number of months
How it works
The calculator uses your annual electricity and gas usage and spreads that usage across the comparison period you choose. It then works out an estimated total cost for the fixed tariff and an estimated total cost for the variable tariff.
For the variable option, it adjusts the current variable unit rates by the percentage changes you enter. This gives you a simple way to model what might happen if variable prices rise or fall over the period.
Why results may be different
Real bills can differ from this estimate for several reasons, including seasonal energy usage, regional pricing differences, supplier discounts, tariff changes during the year and the fact that your future variable price assumptions may not match what actually happens.
- Usage is treated as evenly spread rather than seasonal
- Standing charges can vary by region and supplier
- Exit fees can materially affect short comparison periods
- Future variable rates are uncertain and may move up or down
Who it’s for
- Households deciding whether to fix their energy tariff
- People comparing a renewal offer against a variable tariff
- Anyone wanting a simple break-even style comparison
- Users checking whether exit fees could outweigh savings
Fixed vs variable examples
- A fixed tariff may look better when you expect variable prices to rise and the exit fee is low or zero.
- A variable tariff may look better when rates are already competitive and you expect prices to stay flat or fall.
- Over short periods, even a slightly cheaper fixed tariff can lose out once exit fees are included.
Important note
This tool provides planning estimates only and is not financial advice or a tariff recommendation. Always check the full terms of a tariff, including exit fees and supplier-specific pricing, before switching.
Use the calculator above to compare fixed and variable energy tariffs based on your own usage and assumptions.