Solar Panels for Grain Stores & Crop Barns

Why a grain store or crop barn is one of the best solar roofs on the farm

Of every building on a British arable holding, the grain store and the crop barn give you the most roof per pound. These are among the largest single roofs anywhere on a farm — a modern bulk store or potato shed routinely covers 300 to 3,000 m² of clear-span steel in one unbroken plane. That is exactly the canvas solar PV wants: a wide, low-pitch, unshaded roof with no dormers, no valleys and no chimneys to work around, built on a portal frame that was already engineered to carry snow and wind load. Drop panels onto it and you turn the biggest idle surface on the farm into a thirty-year generating asset.

The complication — and it is the one thing that makes a grain store genuinely different from a poultry shed or a dairy unit — is the load profile. A grain store's defining electrical demand is crop conditioning: the drying and ventilation fans that run for weeks after harvest to bring grain down to a safe storage moisture and then keep it cool and stable through the winter. That is a huge load, but it is a seasonal one, concentrated in late summer and autumn, and it aligns poorly with the long bright days of midsummer when a solar array is generating hardest. Get the design right and a grain-store roof is a superb solar site. Get it wrong — by sizing for a six-week autumn peak that the rest of the year never repeats — and you spend capital on panels that spill their output to the grid for pennies. The whole job on this building type is matching system size to the real, year-round pattern of demand.

Sizing and the roof: what a grain-store array actually looks like

For grain stores and crop barns we typically design systems in the 50 kW to 500 kW band — somewhere between 90 and 920 panels depending on the roof. As a rule of thumb you need around 7–8 m² of clear roof per kW of panels, so the 300–3,000 m² of roof a store offers is rarely the limiting factor. On these buildings the roof is almost never the constraint; the load and the grid connection are. That is the opposite of a small barn conversion, where you size to the roof — here you size to the demand and the export tariff, and the roof has capacity to spare.

Roof structure and cladding

Most modern grain and potato stores are clad in profiled box-profile steel or, on slightly older buildings, fibre-cement sheeting. Both take a standard rail-and-clamp mounting system cleanly, fixing into the purlins without compromising the weatherproofing. The portal frame underneath was sized for agricultural snow and wind loading, so it generally carries the modest extra dead load of a PV array — around 10–15 kg/m² — with nothing more than a short structural appraisal to confirm purlin spacing and frame capacity. We always run that appraisal before any panel goes up; modern steel frames almost always pass, while older or modified stores occasionally need minor strengthening, which we factor into the design up front rather than discovering on the roof.

The asbestos question

Grain stores built before 2000 frequently have asbestos-cement roof sheets. This matters: asbestos cement cannot be drilled or loaded with panels, and under the Control of Asbestos Regulations 2012 only a licensed contractor may remove it. The proven route is a combined strip-and-reclad to modern profiled steel followed by PV on the new roof. On a store that was already heading for a re-roof, the solar business case can part-fund the work you needed anyway — solving a deferred roof problem and an energy upgrade in a single project. If your store has the tell-tale grey-white corrugated sheets, flag it early; it changes the sequence but not the destination.

The economics: a worked example for a grain store

The honest headline for grain stores is that the business case hinges on self-consumption — how much of what you generate you actually use on site — and that depends entirely on what runs in the store outside the autumn drying window. Buildings with a year-round baseload (continuous ambient-air ventilation, refrigerated potato or onion storage, conveyors, lighting, a workshop) self-consume far more of their solar than a bare bulk store that is busy for six weeks and quiet for forty-six.

Take a clearly-illustrative scenario at the middle of the range. Picture a 150 kW array on a large arable bulk store — roughly 275 panels across one clear-span roof of about 1,100 m². A system that size in the UK generates in the order of 135,000 kWh a year, sitting comfortably inside the 45,000–460,000 kWh range these stores produce. Here is how the numbers tend to break down:

Metric	Illustrative figure
System size	150 kW (~275 panels)
Roof area used	~1,100 m²
Annual generation	~135,000 kWh
Self-consumed on site (with steady ventilation / store refrigeration load)	~55%
Surplus exported under the Smart Export Guarantee	~45%
Indicative annual benefit (avoided import + export income)	~£21,000–£24,000
Indicative payback	around 6 years
Annual CO₂ saved	~30 tonnes

That roughly six-year payback is the typical figure for this barn type, and it lands between the faster ~4.5-year returns of a 24/7 poultry shed and the slower ~8-year payback of a heritage or converted barn. The reason it is not faster is precisely the seasonal load: a bare store that exports most of its summer output earns the Smart Export Guarantee rate (typically 4–15p/kWh) on that surplus rather than the much higher avoided-import value of electricity used on site. The single biggest lever you can pull is therefore matching generation to demand:

• Size to the year-round baseload, not the autumn peak. Over-sizing for a six-week drying spike wastes capital — the array spends the other ten months exporting at a low tariff. We model the store's flat baseload first and treat the autumn fans as a bonus the array helps cover, not the number to design around.
• Consider a battery where load is genuinely peaky or evening-weighted. Storage earns its place when surplus would otherwise be exported cheaply, or when the DNO caps your export. It is optional on a store with a steady daytime baseload and valuable on one that is quiet by day.
• Shift movable load into daylight. Running conveyors, cleaning plant, EV charging or a workshop on solar hours lifts self-consumption directly — and every percentage point of self-consumption pulls the payback in.

To pressure-test those figures against your own roof and tariff, our cost guide breaks down price per kW across the full barn range, and the quickest way to a real number is a free desk feasibility built from your half-hourly meter data — start that on our quote page.

Planning and compliance for grain stores and crop barns

The good news for most grain-store owners is that rooftop solar on a working agricultural building is normally Permitted Development under Class A, Part 14 of the GPDO 2015 — no planning application needed, provided the panels don't protrude more than 0.2 m above the roof plane and the relevant capacity and siting limits are met. A modern bulk store on open farmland almost always qualifies. The familiar exceptions — listed buildings, conservation areas, National Parks, AONBs and the Broads — are far less likely to apply to a utilitarian crop store than to a traditional stone barn, but we confirm your building's exact status before committing.

Working around an operational store

Grain stores carry their own on-site safety considerations during installation. Grain handling generates combustible dust, so installs on operational stores observe DSEAR (Dangerous Substances and Explosive Atmospheres Regulations) precautions and grain-dust controls — and we wherever possible schedule the work outside the harvest and conditioning window, when the store is empty and the fans are off. That keeps the install clear of both the dust risk and your busiest weeks of the year.

Grid connection (G99)

Any system above 3.68 kW per phase — which is effectively every grain-store array — needs a G99 connection application to your Distribution Network Operator. Rural networks are frequently capacity-constrained, so this is usually the long pole in the whole project. We submit the G99 application alongside the structural survey to start the DNO clock immediately. Where export capacity is tight, an export-limited or self-consumption-led design — sometimes with a battery and an export limiter — can turn a connection timeline of many months into a few weeks. Because a grain store's seasonal load suits a self-consumption-first design anyway, this often aligns neatly with the fastest route to connection.

Funding that fits a grain store

A grain store on a trading farm is plant on a commercial building, so the funding picture is firmly on the business side of the line:

• 100% Annual Investment Allowance (AIA). Solar PV counts as qualifying plant and machinery, and almost every grain-store install sits well within the £1m annual AIA cap — meaning the whole cost can be written off against tax in year one. For a limited-company farm that is an effective tax saving of up to around 25% of the project cost in the first year, with comparable relief for sole-trader and partnership farms.
• Smart Export Guarantee (SEG). Because grain stores export a meaningful share of their generation outside the drying season, the SEG tariff matters more here than on a 24/7 building. MCS certification is the gateway to it, and we design and certify with SEG eligibility built in.
• Adjacent productivity and devolved grants. Where solar is paired with eligible equipment — a new grain dryer, a ventilation upgrade — it is worth checking productivity grant routes alongside it. Welsh and Scottish farms have their own capital-grant frameworks that can support on-farm renewables, often at more generous intervention rates than the England equivalent.

The one relief that does not apply here is the 0% VAT rate on energy-saving materials — that is for residential dwellings, including converted barns that are someone's home, not for a commercial agricultural store. Our grants and funding page walks through each scheme in full and which ones your specific building qualifies for.

How a grain store compares to other barn roofs

If your holding has more than one building, it is worth knowing where the grain store sits in the pecking order. The portal frame and cladding of a grain store are essentially the same as a general-purpose steel-frame portal barn — the difference is purely the load profile that the conditioning fans impose. And a grain store's seasonal, daytime-leaning demand is the mirror image of a livestock and cattle barn, where steady year-round loads from lighting, scrapers, water heating and (on dairy units) milk cooling deliver much higher self-consumption and a quicker return. On a mixed farm the best plan is often to start with the building whose load best matches solar generation, then bring the big grain-store roof in as a second phase once the connection and the export design are settled.

Frequently asked questions

How big a solar system can my grain store take?

Almost always bigger than your electricity bill justifies — which is the point. Grain and potato stores carry some of the largest roofs on any farm, 300–3,000 m² of clear span, so at roughly 7–8 m² per kW the roof can host anything from a 50 kW array up to 500 kW. The real question is never "how much roof?" but "how much load?" We size to your year-round demand and export tariff rather than filling every square metre, because a panel that only ever exports at the SEG rate earns far less than one offsetting electricity you'd otherwise buy.

My drying fans only run in autumn — does solar still make sense?

Yes, but the design has to respect that seasonality. The autumn drying and conditioning peak doesn't line up with summer generation, so we don't size the array to chase it. Instead we model the store's steady baseload — ventilation, refrigerated storage, conveyors, lighting — size the system to that, and treat the array's contribution to the autumn fans as a welcome extra. Where the load is genuinely concentrated and the rest of the year is quiet, a battery or an export-led design carries the surplus, and the Smart Export Guarantee pays for what you can't use on site.

Do I need a battery on a grain store?

Not necessarily. A store with a steady daytime or refrigerated baseload uses most of its generation directly, so a battery is optional. Storage earns its keep in two situations specific to this building type: where the load is so seasonal that summer output would otherwise be exported at a low tariff, and where the rural DNO limits your export capacity and you'd waste surplus without somewhere to put it. We size storage only where the numbers justify it, using your half-hourly meter data — never as a default add-on.

Can solar be installed while the store is full of grain?

We strongly prefer to install when the store is empty and the fans are off — typically outside the harvest and conditioning window. Grain handling creates combustible dust, so work on an operational store has to observe DSEAR and grain-dust precautions, and an empty store removes that risk entirely while giving the install team clear, safe access. Scheduling around your cropping calendar is part of how we plan the project, so the array goes up without ever getting in the way of getting the crop in.