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.
| Band / figure | Rate |
|---|---|
| Installation cost | confirmed net quote entered |
| Bill saving | quote or survey assumption entered |
| Energy-price change | entered by you |
| Grant eligibility | not assessed |
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 or price scenarios quickly.
- When you need a simple estimate before requesting installer or supplier quotes.
- When a tariff is about to change and you want to model the bill impact.
A realistic UK planning example
Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.
| Input | Value |
|---|---|
| Upgrade A | Solar panels |
| Upgrade A net upfront cost after confirmed grant (£) | £500 |
| Upgrade A first-year bill saving from quote (£) | 5 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. Then rerun the tool with one input adjusted.
How to read your results
Higher Present-Value Option
The figure produced by this output for the inputs you entered. Change one variable at a time if you want to see what drives it.
Upgrade A
The figure produced by this output for the inputs you entered. Change one variable at a time if you want to see what drives it.
Upgrade A NPV
The figure produced by this output for the inputs you entered. Change one variable at a time if you want to see what drives it.
Upgrade A Nominal Lifetime Net
The figure produced by this output for the inputs you entered. Change one variable at a time if you want to see what drives it.
Upgrade A Simple Payback
How long it takes to recover the upfront cost through the ongoing saving or income you entered.
Upgrade B
The figure produced by this output for the inputs you entered. Change one variable at a time if you want to see what drives it.
Upgrade B NPV
The figure produced by this output for the inputs you entered. Change one variable at a time if you want to see what drives it.
Upgrade B Nominal Lifetime Net
The figure produced by this output for the inputs you entered. Change one variable at a time if you want to see what drives it.
Upgrade B Simple Payback
How long it takes to recover the upfront cost through the ongoing saving or income you entered.
NPV Difference A minus B
The figure produced by this output for the inputs you entered. Change one variable at a time if you want to see what drives it.
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 the current tariff without testing a higher unit rate.
- !Forgetting the standing charge when comparing annual bills.
- !Treating the result as a supplier quote.
- !Using optimistic savings figures for an upgrade without a written estimate.
What to do next
- Run the same scenario with a 10% higher unit rate.
- Compare this result with a related energy calculator before requesting installer quotes.
- If you are evaluating an upgrade, rerun with actual quote figures.
- Set a reminder to rerun the calculation when your tariff renews.
Frequently asked
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