Example result based on the prefilled values.
Higher Present-Value Option
Upgrade A — Solar panels
Upgrade A
Solar panels
Upgrade A NPV
£2,304.52
Upgrade A Nominal Lifetime Net
£5,808.43
Upgrade A Simple Payback
11 years
Upgrade B
Solar panels
Upgrade B NPV
£-994.83
Upgrade B Nominal Lifetime Net
£1,344.75
Upgrade B Simple Payback
13 years
NPV Difference A minus B
£3,299.34
Continue your plan
Useful next calculations
Rates & sources
Quote-led present-value comparison. The calculator does not supply installation costs, grants, tariffs or saving claims; all financial assumptions are entered by the user.
Source: GOV.UK — find energy grants — check the linked guidance and any live quote before acting.
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.
Upgrade A
Solar panels
Upgrade A net upfront cost after confirmed grant (£)
£500
Upgrade A first-year bill saving from quote (£)
25 years
Upgrade A annual maintenance/running-cost increase (£)
£500
After entering these figures, review higher present-value option, upgrade a and upgrade a npv 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
Higher Present-Value Option
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.
Upgrade A
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.
Upgrade A NPV
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.
Upgrade A Nominal Lifetime Net
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.
Upgrade A Simple Payback
The payback period shows how many months or years it takes to recover the upfront cost through ongoing savings or income. Compare it against how long you plan to stay in the property or use the product before deciding whether the investment makes financial sense.
Upgrade B
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.
Upgrade B NPV
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.
Upgrade B Nominal Lifetime Net
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.
Upgrade B Simple Payback
The payback period shows how many months or years it takes to recover the upfront cost through ongoing savings or income. Compare it against how long you plan to stay in the property or use the product before deciding whether the investment makes financial sense.
NPV Difference A minus B
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 comparator is deliberately quote-led. For each upgrade, enter the price you would actually pay after any confirmed grant, the first-year bill saving from the survey or quote, annual running or maintenance cost, comparison life and saving degradation.
The nominal lifetime net adds the modelled annual net savings and subtracts the upfront cost. NPV discounts those future savings using the rate entered. Simple payback is the first whole year when cumulative nominal savings recover the net upfront cost.
Energy prices, weather, occupancy, export tariffs, equipment performance and maintenance are uncertain. Financing interest, tax, replacement components, residual value, carbon savings and interactions between two upgrades are not modelled. Compare like-for-like scopes and verify certification, warranties and grant conditions independently.
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
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