Commercial solar ROI
Payback period tells you when you break even. Return on investment tells you what the asset is actually worth over its life — a different, more complete question.
Why ROI and payback tell different stories
A system with a longer payback can still have a better lifetime ROI than one with a shorter payback, if it degrades more slowly, needs less maintenance, or carries a stronger warranty. Payback is a threshold; ROI (or a full NPV/IRR calculation) accounts for everything that happens after that threshold too.
What a fuller ROI picture needs
- Capital cost, including everything the scope comparison in a proper proposal review would surface — not just the headline price.
- Annual generation and its expected degradation over the system's life (typically specified as %/year in the proposal).
- Ongoing costs: O&M, monitoring, inverter replacement (inverters typically don't last as long as panels), insurance.
- How electricity prices are assumed to move over the system's life — a fixed assumption versus an escalating one changes the picture substantially.
- Financing cost, if the system isn't purchased outright.
- Available capital allowances or other tax treatment — which depends on your specific business and financing structure. We don't provide tax advice; confirm current treatment on GOV.UK or with your accountant.
Board-pack-level modelling
A full NPV/IRR/sensitivity model is a heavier tool than most businesses need for an initial decision, and it's not something we generate automatically today. Our proposal review focuses on making sure the inputs to that kind of model — price, generation, assumptions, scope, lifetime costs — are accurate and comparable across proposals first. Get that right before the spreadsheet matters.
Have proposals in hand and want the underlying numbers checked? Upload them for review.