Farm Solar Feasibility Study: What Is Actually in the Report (2026)

Before a single panel is ordered, a serious rooftop project on a working farm should start with a desk-based study that answers one question honestly: does this stack up, building by building, over 25 years? A good report is not a sales brochure with a payback figure bolted on the back — it is an engineering and financial document you could hand to your accountant, your bank, and the DNO. Here is exactly what should be inside it, and how the numbers are actually produced.

What a desk-based feasibility study is — and what it is not

A farm solar feasibility study is a remote, evidence-led assessment that uses your meter data, satellite imagery, roof geometry and irradiance datasets to model whether solar is technically and financially viable on your holding. It is deliberately distinct from a full site survey. The feasibility stage tells you whether to proceed and roughly at what scale; the site survey, carried out later by an MCS installer, confirms rafter spacing, purlin condition, cable routes and inverter siting before installation.

The reason the two are separated is cost and risk. A desk study can be turned around in days from data you already hold, so you are not paying for scaffolding and a roof inspection on a scheme that was never going to work. If the study says yes, the survey then de-risks the build. If it says no — or “yes, but only on the grain store, not the dairy” — you have saved yourself a wasted day and an awkward quote.

System sizing, building by building

Few farms are a single roof. You typically have a mix — a dairy parlour running 18 hours a day, a grain store that draws heavily for a few weeks of drying, machinery sheds, and perhaps a barn that is structurally marginal. The report sizes a separate array for each viable roof rather than quoting one headline kWp.

For every building the study records pitch, orientation (azimuth), available unshaded area, and an estimated structural allowance. South-facing pitches at 15–35° are ideal, but east–west splits often suit a farm better because they spread generation across the morning and evening when livestock and refrigeration loads are highest. The output is a per-building kWp figure, a panel count, and an indicative inverter configuration — the raw inputs everything downstream depends on.

How annual yield is actually modelled

This is where a credible study earns its fee. Annual yield is not “kWp × 950” on the back of an envelope. The report should model generation in dedicated PV software — typically PVSyst — using a defined chain of inputs:

• Irradiance data for your exact location, drawn from datasets such as PVGIS or Meteonorm, not a national average.
• Array geometry — the pitch and azimuth captured per building above.
• Shading analysis from a 3D horizon and near-object model, picking up grain silos, neighbouring barns, trees and chimney stacks that clip early-morning and winter output.
• Soiling losses — agricultural roofs gather dust, pollen and bird fouling faster than a suburban house, so a realistic soiling factor (often 2–4%) is applied.
• System losses — inverter efficiency, DC and AC cabling, temperature derating and module mismatch, usually totalling a 12–18% gap between nameplate and delivered output.
• Degradation — panels lose output gradually, so the model applies roughly 0.4–0.5% per year, which is what makes the 25-year figure meaningful rather than year-one flattered.

The deliverable is an honest first-year yield in kWh and a year-by-year generation curve, not a single optimistic number.

Self-consumption: the figure that decides the economics

On a farm, the single most important number is not how much you generate — it is how much you use on site. Every kWh you consume directly displaces grid electricity at roughly 25–28p, whereas every kWh exported earns only a Smart Export Guarantee (SEG) rate of around 8–15p. The gap between those two figures is the whole game.

To calculate the self-consumption ratio properly, the study overlays your modelled half-hourly generation profile against your actual demand. The best input is your half-hourly meter data (the HH data your supplier holds for most non-domestic supplies); where that is not available, a load profile is built from your annual consumption and known load patterns. The report then states what proportion of generation is used on site versus exported — and that ratio drives every financial figure that follows. A dairy or cold store with steady daytime load might self-consume 70%+; a barn with little daytime demand might be under 40%, which materially changes the case.

The 25-year discounted cash flow

A feasibility report worth reading models the economics over the full asset life, not just a simple payback year. The discounted cash flow (DCF) brings every future saving and export receipt back to today’s money so you can compare it fairly against the capital outlay. Typically it presents the headline metrics together: simple payback, internal rate of return (IRR), net present value (NPV) and 25-year net benefit, with an assumed electricity-price inflation that should be stated and sensitivity-tested rather than hidden.

Crucially, the DCF should model the way the project is actually paid for, because that changes the cash position dramatically:

• Outright capital — the simplest case; full cost up front, all savings yours from day one. See our cost guide for indicative ranges.
• 100% AIA — UK farm solar generally qualifies for the Annual Investment Allowance, letting a trading farm deduct 100% of qualifying plant cost against taxable profit in the year of spend (within the £1m annual cap). For a profitable farm this can recover a large slice of the cost through reduced tax — a genuine difference-maker the DCF should show explicitly.
• Asset finance — spreading capital over a term so the energy saving services the repayment, often producing positive cash flow from year one.
• PPA — a power purchase agreement where a third party funds the system and you buy the generation at a fixed rate; zero capital, but a lower lifetime saving.

A good report runs the numbers under at least two of these structures so you can see, in cash terms, which route suits your tax position and appetite for capital.

Grid connection: the G99 timeline forecast

The grid is where farm schemes stall, so the study should forecast it rather than ignore it. Connections are governed by the DNO under Engineering Recommendation G99. Smaller arrays may qualify for a connect-and-notify route, but larger farm systems usually require a full G99 application and a connection offer before energisation — and that process can take weeks to several months depending on local network capacity.

The report should flag the likely application route, indicate whether export limitation might be needed to secure a connection without costly reinforcement, and give a realistic timeline. Under the Class A permitted development rights (Part 14, GPDO 2015), rooftop solar up to 1 MW can be installed without a full planning application since the December 2023 uplift — but permitted development is not the same as a grid connection, and the study should keep the two separate in your mind.

The asbestos-cement roof flag under CAR 2012

Many agricultural roofs built before the late 1990s are asbestos-cement (typically corrugated “Big Six” sheeting). This is a feasibility red flag the report must raise. You cannot mount solar by drilling into, or disturbing, asbestos-cement without triggering duties under the Control of Asbestos Regulations 2012 (CAR 2012) — and a degraded sheet often cannot safely carry a 25-year array regardless.

Where an asbestos roof is identified, the study should recommend a combined re-roof plus solar approach: licensed removal of the asbestos, a new profiled-steel roof, then the array. It is more capital up front, but it removes a liability, resets the roof’s lifespan to match the panels, and is frequently the only compliant way forward. The report should price this scenario rather than quietly assuming a sound roof.

Turning the report into action

A complete feasibility study leaves you with per-building sizing, a PVSyst-grade yield model, a self-consumption ratio built on your own data, a 25-year DCF across realistic funding routes, a G99 timeline, and any roof-condition flags resolved. That is the document that lets you decide with confidence — and it is what we deliver as standard. If you would like a study tailored to your holding, you can also explore grants and funding and our agricultural solar installers once the numbers stack up.

Ready to find out whether your roofs stack up? Request your farm feasibility study.