Check the assumptions behind your solar payback.
Projected solar savings are only as useful as the assumptions underneath them. A quote should let you understand how the installer reached the headline figure.
We keep a clear line between what the document says, what we calculate and what still needs checking.
What to check
- Predicted annual generation
- Household electricity use
- Solar used in the home
- Import electricity price
- Export tariff
- Battery charging assumptions
Why payback estimates differ
Two installers can quote the same hardware but show different financial returns because they assume different tariffs, export income or household usage. Comparing those assumptions can be just as important as comparing the hardware.
Use independent calculators as a sense check
Energy Saving Trust provides a solar calculator that estimates costs and savings using property and household information. It can be a useful independent reference alongside an installer proposal.
Sources for this guide
We use public consumer guidance and official registers where they help answer the question. These organisations do not endorse QuoteCalm and we do not use their logos as trust badges.
Guidance, prices and schemes can change. Follow the linked source for the latest position if the detail is time-sensitive.
Frequently asked questions
Is a solar payback period guaranteed?
No. It is an estimate that depends on future generation, usage, tariffs and system performance.
What should I ask if the savings calculation is unclear?
Ask the installer to show the annual generation estimate and the electricity price, export tariff and household-use assumptions behind it.
We keep a clear line between what a quote says, what can be calculated and what still needs checking. We do not accept payment from installers to change the outcome of a quote check.
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