Rates & sources
UK energy unit rates vary by region and supplier. Ofgem publishes a price cap refreshed each quarter.
Source: Ofgem — Energy price cap — figures refreshed at the start of each tax year.
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When to use this calculator
- Before switching supplier, upgrading equipment, or comparing energy-saving changes.
- When you want to test different usage assumptions or price scenarios quickly.
- When you need a simple estimate before requesting installer or supplier quotes.
- When you are evaluating solar panels, a heat pump, or insulation and want to check the payback period before spending.
- When your tariff is about to change and you want to quickly model the impact on your annual energy bill.
A realistic UK planning example
Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.
Annual Electricity Usage (kWh)
35
Annual Gas Usage (kWh)
35
Your Current Tariff
Ofgem price cap (standard)
Electricity Unit Rate (p/kWh) — if fixed
5%
After entering these figures, review annual electricity cost, annual gas cost and total annual bill together rather than in isolation — each metric tells a different part of the story. Then rerun the tool with one input adjusted to see which variable has the biggest effect on all three outputs before you settle on a plan.
How to read your results
Annual Electricity Cost
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Annual Gas Cost
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Total Annual Bill
This is the headline outcome of the calculation, but it is most useful when read alongside the supporting metrics below it rather than in isolation. Try changing one input at a time and watching how this total moves to understand which driver has the biggest impact.
Monthly Average
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Saving vs Price Cap
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Method & assumptionsAuthoritative sources
This calculator estimates your annual domestic energy bill using the Ofgem price cap rates applicable from Q2 2025: 24.50p per kWh for electricity, 6.24p per kWh for gas, a daily electricity standing charge of 61.64p, and a daily gas standing charge of 31.65p. These rates reflect the standard variable tariff cap for a typical single-register meter in England, Scotland, and Wales. Daily standing charges are annualised by multiplying by 365, and unit costs are based on your stated annual consumption in kWh. If you select a fixed tariff, your own unit rates replace the cap rates, though cap-level standing charges are retained for comparison purposes.
The Ofgem price cap is reviewed every three months — in January, April, July, and October — based on wholesale energy market prices. The rates used here are indicative for Q2 2025 and will change in subsequent quarters. For your most accurate bill, always refer to the actual rates on your latest bill or your supplier's current tariff statement. This tool is designed for illustrative budgeting purposes and should not be used as the sole basis for switching decisions.
Common mistakes
- !Using optimistic assumptions without testing a more cautious scenario as well.
- !Comparing outputs from different tools without checking that the inputs match.
- !Treating the result as a final quote instead of a planning estimate.
- !Using the current tariff rate without accounting for future price changes, which can make payback calculations look more favourable than they really are.
- !Forgetting to include the standing charge when comparing annual energy costs, which can be a significant portion of a typical bill.
What to do next
- Run the same scenario with a 10% higher unit rate to see how your figures would look if prices rise.
- Compare this result with a related energy or insulation calculator before requesting installer quotes.
- Use the linked guides to understand export tariffs, grant eligibility, or supplier comparison approaches.
- If you are evaluating an upgrade, get at least two installer quotes and rerun this calculator with the actual cost figures before committing.
- Set a reminder to rerun the calculation when your tariff renews, so the payback estimate stays accurate.
Frequently asked
Use arrow keys to navigate items, Enter or Space to expand/collapse.
End-of-article next steps
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