The short answer
Simple payback divides an upfront cost by an annual saving. It is a screening calculation, not a complete investment forecast, and it becomes misleading when costs or savings are defined inconsistently.
Make a deliberately simple example
If an illustrative installation costs £12,000 and saves £1,000 per year, simple payback is 12 years. Neither figure is a SolarIQ quotation or a claimed household outcome.
The arithmetic assumes that annual saving stays constant and ignores maintenance, replacements, financing and the time value of money. A fuller assessment needs those effects explicitly.
Avoid counting export twice
Check whether the displayed annual saving already includes export credit. If it does, adding export income again overstates the benefit.
Use total electricity costs on the same basis before and after installation. State whether standing charges are included, and do not treat a charge that remains payable as an avoided cost.
Test the additional battery separately
For an illustrative £4,000 additional battery cost and £250 additional annual benefit, simple incremental payback is 16 years. This does not establish its service life or warranty coverage.
Keep the panels, tariffs and demand fixed in the comparison. Backup value is a separate decision and should not appear as invented energy-bill savings.
Keep the downside visible
Repeat the calculation with lower savings and with plausible additional costs. Ask which assumptions most affect the result and which are supported by evidence.
SolarIQ’s long-term projections are illustrative scenarios with stated exclusions. Request a surveyed installation quotation and review the methodology before using a forecast to make a purchase decision.
Before your assessment
Bring these questions with you.
- Total installed cost with a consistent scope.
- Annual saving with export counted once.
- Separate incremental battery comparison.
- Maintenance, replacement and financing assumptions.