Receiving a 35-page feasibility dossier can feel like homework. It is not. A well-structured report is designed to be read in layers — from verdict to detail — so you can decide whether to fund the next stage of work without becoming a solar engineer.
This guide gives estates directors, asset managers, and consultants a practical reading order for UK commercial rooftop feasibility reports.
Start with the verdict, not the appendix
Open the executive summary. You are looking for four things:
- Recommendation — pursue, pursue with conditions, or do not pursue.
- Indicative capacity — kWp proposed and whether it is geometry-limited or economics-limited.
- Headline financials — payback, NPV, or annual savings at stated assumptions.
- Top flags — structure, grid, planning, or data gaps that could change the outcome.
If the verdict is “do not pursue,” the rest of the report explains why. You may still read on to understand whether future roof works or tariff changes could reopen the case, but you should not book structural surveys on the strength of a negative verdict.
If the verdict is positive, treat the remainder as the evidence pack — useful for board papers and tender briefs. See solar investment board paper for how to lift material across.
Compare structure against our example report if you want a reference layout.
Check the site basics before the numbers
Before trusting yield, confirm the report describes the right building. Address, roof identification, usable area, and exclusions should match your knowledge of the site.
Ask:
- Does the layout avoid plant, skylights, and fire routes you know exist?
- Is the pitched or flat roof characterisation correct?
- Are multiple roof areas handled separately where needed?
Errors here cascade through generation and financials. Catching a wrong roof plane early saves embarrassment in committee.
Read generation with appropriate scepticism
Locate the annual kWh figure and the method behind it. Feasibility-grade estimates are screened estimates — generation figures have been checked against twelve months of metered output from an operating commercial installation. — not meter-perfect forecasts.
Scrutinise:
- Shading — Are nearby buildings or equipment modelled?
- Losses — Do assumptions look standard or optimistic?
- Degradation — Is year-one versus lifetime average clear?
Our methodology explains how Stage1Energy approaches modelling. For deeper context, read how accurate solar generation estimates are.
If generation is high but the roof has obvious obstructions not mentioned, challenge the provider before the board sees it.
Stress-test the financial section
Payback is a hook, not the whole story. Read the cashflow or NPV tables if present — they reveal whether later-year inverter replacement or export-heavy years weaken the case.
Work through assumptions in this order:
Self-consumption split. How much load data underpins it? Estimated tenant consumption should be flagged as weaker than half-hourly meter data.
Electricity tariff. Is the import price realistic for your supply contract? A feasibility using outdated p/kWh figures can misstate savings by thousands annually.
Export price. If a large share is exported, small changes in SEG or PPA rates move payback materially.
Capex basis. Feasibility often uses benchmark £/kWp unless quotes exist. Note whether VAT, scaffolding, and grid connection are included or excluded.
Incentives. Confirm nothing expired or inapplicable is baked in — particularly relevant in commercial solar feasibility in 2026.
Adjust one variable at a time mentally. Robust projects survive moderate pessimism. Fragile ones fail when you shave 5% off self-consumption — and you want to know that before surveys, not after.
Treat engineering flags as a to-do list
Engineering sections at feasibility stage are screening flags, not sign-offs. Read them as questions for qualified professionals:
- “Portal frame — confirm capacity” means book a structural engineer.
- “Ballast loading may be tight” means do not assume penetration-free mounting is automatic.
- “Roof membrane age uncertain” means coordinate with your roofing contractor.
The boundary between feasibility and structural survey is important — see feasibility vs structural survey. Do not treat cleared flags as substitutes for surveys.
Understand grid and planning limits
Grid screening tells you whether connection is likely to be routine or contentious. If the report says G99 with export limitation, expect timeline and cost in the risk register even if the headline payback looks fine.
Planning notes should state permitted development versus full application. If the building is listed or in a sensitive area, feasibility should say so plainly. “Low risk” without evidence is not helpful.
Read limitations before you forward the PDF
Credible reports state what they are not. Feasibility is not design, procurement, or construction documentation. Data gaps — no half-hourly load, ageing imagery — should be listed.
If limitations are missing, add your own cover note when circulating internally. Boards trust authors who know what they do not know.
Map findings to next steps
End with a simple action list:
| Verdict | Typical next step |
|---|---|
| Pursue | Brief installers; commission structural survey |
| Pursue with conditions | Resolve stated conditions first |
| Marginal | Revisit when tariff, load, or roof works change |
| Do not pursue | Archive; note trigger for reassessment |
If you need a faster initial filter on other sites, free screening precedes full dossiers. When the reading confirms a strong case, site assessment at £1,250 per site is the standard depth for UK commercial rooftops.
Common reading mistakes
Treating feasibility as a quote. It is independent analysis — compare feasibility study vs installer quote.
Focusing on kWp alone. Larger is not always better if export is discounted or grid limits apply.
Ignoring conditions. “Pursue if structural survey confirms” is not a green light until survey returns.
Skipping the flags because payback looks good. Engineering and grid issues are how projects stall after board approval.
Closing thought
Reading a feasibility report well means extracting a decision and a prioritised action list — not validating every cell in a spreadsheet. Verdict first, assumptions second, flags third.
For section definitions, see what is in a solar feasibility report. For the service behind Stage1Energy dossiers, visit commercial solar feasibility.