Check the assumptions behind your solar payback.
Projected solar savings are only as useful as the assumptions underneath them. A quotation should make it possible to understand how the installer reached the headline figure.
We separate information in the document from calculations and from anything the quote does not tell us.
What to check
- Predicted annual generation
- Household electricity use
- Self-consumption rate
- 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 the assumptions is therefore 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 is a useful independent reference alongside an installer proposal.
References for this guide
We use relevant public consumer guidance and registers as reference points. These organisations do not endorse QuoteCalm and we do not use their logos as trust badges.
Guidance, prices and schemes change. Follow the linked source for the current position before relying on time-sensitive information.
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 provide the annual generation estimate and the import, export and self-consumption assumptions used.
We aim to distinguish information stated in a quotation, calculations we can reproduce, public consumer guidance and things that cannot be known without a property-specific assessment. We do not accept payment from installers to change the outcome of a quote check.
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