Every commercial solar project eventually meets a gate: a board, an investment committee, a client sign-off, or a landlord’s asset strategy forum. The business case is what gets you through that gate — or stops you spending on surveys for a roof that was never viable.
For UK commercial rooftop PV, the business case is not a slide with a payback number. It is a structured argument that the proposed array is technically plausible, financially worthwhile, and proportionate to the risks still outstanding at this stage.
What the business case must answer
Decision-makers need four questions answered in one document:
- What are we proposing? Indicative capacity, layout, and generation on this specific roof.
- What does it earn or save? Self-consumption value, export income, and 25-year cashflow in pounds, with assumptions named.
- What could stop it? Engineering flags, grid route, planning risk, and structural questions still open.
- What do we do next? Pursue, pursue with conditions, or do not pursue — with the next spend item identified.
A commercial solar feasibility study is designed to answer all four before structural engineers, DNO consultants, or installers are engaged. That is the difference between a business case built on evidence and one built on optimism.
Recommended structure for a board paper
There is no single template every UK corporate uses, but strong papers follow a consistent arc.
Executive summary. One page: verdict, headline metrics (payback, NPV at corporate discount rate, IRR), capex band, and the single biggest risk.
Site and load context. Building type, occupancy pattern, current annual consumption and cost, and why this roof was shortlisted.
Technical summary. Usable area, orientation, feasibility-grade kWp, annual kWh yield, and how generation was modelled. Reference our methodology page and dossier assumptions, or equivalent transparency from another provider.
Financial analysis. 25-year cashflow table or chart, payback, NPV, IRR, and sensitivity on generation, self-consumption, and tariff. Our commercial solar financials hub explains how these metrics relate.
Commercial structure. For landlords: who benefits, lease implications, and whether tenant engagement is required. For owner-occupiers: which cost centre captures savings.
Risks and open items. Structure, wind loading, roof condition, G98/G99 route, export limits, planning. Each flag should state what full survey would cost and what programme it adds.
Recommendation and next steps. Approved feasibility spend, tender route, or park the site.
Include a short funding and approval route — operational capex, capital project code, or landlord contribution — so the committee knows what it is authorising beyond the solar case itself.
Deeper guidance on payback and NPV sits in commercial solar payback in the UK and commercial solar NPV explained.
Financial metrics the board will expect
Finance stakeholders rarely approve on payback alone. Expect to present:
- Simple payback — intuitive, but insufficient alone.
- NPV — at the organisation’s discount rate, with sensitivity.
- IRR — comparable against other capital requests.
- Capex — benchmark installed cost, with scope defined.
The relationship between these metrics is covered in solar IRR vs payback for commercial projects. The underlying annual series comes from a 25-year solar cashflow model.
Self-consumption assumptions often make or break the case. See self-consumption and export for commercial solar for how load match drives value.
Risks that belong in the business case
Financial metrics without engineering context create false confidence. A business case should acknowledge screening-level flags, not bury them.
Typical items include portal frame capacity, ballast or penetration approach, asbestos or fragile roof coverings, DNO export constraints, and whether permitted development applies. These are not reasons to reject solar — they are reasons to budget the right next step.
Feasibility flags risks; it does not replace detailed design or structural sign-off. That boundary should appear explicitly so the board knows what it is approving.
Independence and sourcing
Boards and lenders increasingly challenge solar business cases sourced from installers who will profit from a proceed decision. Independent feasibility — with formulae, tariff sources, and yield inputs visible — withstands scrutiny better.
Ask whether the document shows its workings. The example report demonstrates what that looks like for a real UK commercial roof: verdict, financials, engineering flags, and calculation trail in one 29-page dossier. For how an independent solar feasibility study produces those numbers, see the full guide.
Portfolio vs single-site business cases
On a single warehouse, the business case is site-specific. Across a portfolio, the case often has two layers: a ranked shortlist from screening, then full feasibility on the top sites.
Batch feasibility lets you compare commercial solar payback and NPV on a consistent basis rather than reconciling incompatible installer proposals. Assessments are booked in order of receipt. Capacity is limited; if a requested date cannot be met, we will say so before taking payment. The same standard applies whether the board wants options on one site or many.
How Stage1Energy supports the business case
The site assessment is a fixed-fee, board-ready feasibility dossier at £1,250 per site, delivered in five working days. It is written to drop into a business case with minimal rework: financials, engineering flags, and sourced workings in one document.
If you need a faster steer on whether a case is worth building, free screening returns a short verdict in three working days.
A strong commercial solar business case does not oversell the roof. It gives decision-makers enough rigour to approve the next pound of spend — or to close the file and move on.
Where ESG or net-zero targets are in play, keep carbon savings in the narrative separate from the core financial cashflow unless your organisation has a formal carbon price. Mixing the two without a stated basis makes IRR comparisons with other projects misleading.
To model these metrics for a named UK commercial roof, see solar feasibility study cost in the UK or start with free screening.