Warehouses: Commercial Solar PV

Why commercial solar PV makes sense for warehouses and industrial units

A large, flat or shallow-pitched steel-portal roof is the single best canvas for solar PV in the UK, and warehouses have that roof in abundance. Where an office might fit 30 to 40 kWp on a modest footprint, a distribution shed or industrial unit routinely carries several hundred kilowatts of panels with room to spare. That scale is what makes the numbers work. The bigger the array, the lower the cost per kilowatt-peak, and the more of your grid bill you can permanently displace.

Warehouse roofs are also, by design, unshaded and uncluttered. There are rarely dormers, chimneys, or parapets breaking up the plane, and the buildings tend to sit on open industrial estates rather than in dense town centres. That means fewer compromises on panel layout and orientation, and a yield model that behaves close to its theoretical best. Most metal warehouse roofs take non-penetrative clip-fix mounting that clamps to the standing seam or trapezoidal profile without a single roof penetration, so the roof warranty stays intact.

The demand side is the other half of the case. Forklift and materials-handling-equipment charging, dock levellers, LED high-bay lighting, and any on-site refrigeration or chilled storage create a strong daytime baseload, and in a 24-hour operation that load runs round the clock. Solar generates during the working day, which is exactly when a busy warehouse is drawing hardest, so a high share of what the array produces is consumed on site and never sold cheaply back to the grid. Self-consumption is the factor that actually determines commercial payback, and warehouses tend to score well on it.

The warehouse load profile and self-consumption

Commercial PV is sized from your consumption shape, not your roof area. The question that matters is not how many panels fit, but how much of their output you will use directly. For a warehouse the answer is usually a good deal, because the demand is broad and daytime-weighted rather than spiky.

A typical single-shift distribution unit running 08:00 to 18:00 draws steadily through the day: lighting on from open, MHE batteries on charge, compressors cycling, and offices and welfare areas adding a smaller constant load. A building like that commonly achieves 55 to 75 per cent self-consumption from a well-sized array with no battery at all. Add a second shift, cold storage, or a chilled distribution operation and the daytime baseload rises, pushing self-consumption higher still and shortening the payback.

The features that make warehouses well suited to solar are worth spelling out:

• Large, unshaded steel-portal roofs give the most usable array area of any commercial building type.
• Clip-fix, non-penetrative mounting suits standing-seam and trapezoidal metal roofs and preserves the existing roof warranty.
• Forklift charging, materials-handling equipment and refrigeration create strong daytime and often round-the-clock baseload.
• A landlord-and-tenant split, common in the sector, means a Power Purchase Agreement or rent-a-roof structure is often the cleanest route to getting solar on the roof.

Where a meaningful part of demand falls outside daylight, evening dispatch, overnight refrigeration, or weekend picking, battery storage becomes worth modelling. It typically lifts self-consumption from the 55 to 75 per cent range up to 80 to 95 per cent and adds a quarter to two-fifths onto annual savings, at the cost of a longer payback. We model the array with and without storage, and design every system to be battery-ready so you can add cells later without reworking the electrics. You can compare the two side by side on the savings calculator.

System sizing for a warehouse or industrial unit

As a rule of thumb, 1 kWp of PV needs roughly 5 to 6 sqm of unshaded roof and generates about 900 to 1,000 kWh a year in the UK. A warehouse roof of 600 to 3,000 sqm therefore supports a system in the region of 100 to 500 kW, made up of somewhere between 185 and 920 panels depending on module wattage and layout. That is the bracket most warehouse and industrial-unit projects fall into.

At that scale a warehouse array generates roughly 92,000 to 460,000 kWh a year and displaces in the order of 21 to 106 tonnes of CO2 annually, useful evidence when customers or investors start asking Scope 2 questions. The design target is annual generation equal to about 60 to 85 per cent of your current consumption, which maximises self-consumption while avoiding a large volume of low-value export. We size from your half-hourly meter data rather than roof area alone, so the array is matched to how the building actually uses power across the day and the year.

Roof area is the ceiling, not the target. If your demand is high enough to justify more than the roof will carry, we can look at combining rooftop PV with a solar carport over the yard or a ground-mounted array on spare land. If demand is lower than the roof could support, we size to consumption and, where it suits you, plan the array so a later expansion is straightforward.

A worked cost and payback example

Warehouse systems in the 100 to 500 kW range typically carry a project value of around £85,000 to £425,000 fully installed, before any tax relief. Cost per kilowatt-peak falls as the system grows, so a larger array is materially cheaper per unit of capacity than a small one. For a full breakdown of what is and is not included at each size, see the cost guide and the grants and funding routes.

The table below sets out three indicative points across the warehouse bracket. Figures are illustrative and depend on roof, tariff and load profile; a real proposal comes from your own meter data.

System size	Roof area (approx)	Annual generation	Indicative installed cost	Typical payback
110 kW	650 sqm	100,000 kWh	£95,000	6 to 7 years
250 kW	1,500 sqm	230,000 kWh	£210,000	6 years
450 kW	2,700 sqm	415,000 kWh	£370,000	5 to 6 years

Take the 250 kW case. A distribution unit generating around 230,000 kWh a year and consuming most of it during working hours might save in the region of £45,000 to £55,000 a year against grid electricity at current commercial rates, plus a smaller sum from exporting surplus under the Smart Export Guarantee, which pays roughly 4p to 15p per kWh. On an installed cost near £210,000 that puts simple payback at about six years, the typical figure for the sector. Because 100 per cent Annual Investment Allowance lets a profitable company deduct the full capital cost from taxable profit in year one, the effective net cost for a limited company is closer to three-quarters of the headline price, which pulls the real payback in further. VAT is reclaimable in the normal way for a VAT-registered business.

The panels carry a 25-year performance warranty. Once the system has paid for itself in around six years, it goes on producing near-free power for another 15 to 20, and that saving grows in value every time grid prices rise. Run your own numbers on the savings calculator, or ask for a modelled figure through the free desk feasibility.

Planning, compliance and grid connection

Most warehouse rooftop PV falls under Permitted Development, Class A Part 14 of the GPDO, so no planning application is usually required, subject to the standard size and siting limits. Industrial estates rarely sit in conservation areas, which removes the most common planning complication. We confirm the planning route as part of the feasibility study and handle any application that turns out to be needed.

Two structural points matter on large sheds. Roofs over about 1,000 sqm frequently need a structural survey to confirm they can carry the additional dead load of the panels and mounting, and to check wind-uplift performance across an exposed industrial site. Second, any building constructed before 2000 should have an asbestos management survey before work starts, because older industrial roofs can contain fibre-cement sheeting. Neither is a reason not to proceed; both are reasons to survey properly up front rather than discovering a problem mid-install.

Grid connection is usually the critical path, so it drives the timeline more than the physical install does. Small systems under roughly 50 kW can sometimes use the faster G98 or G99 fast-track, but a warehouse array is almost always large enough to need a full G99 application to your Distribution Network Operator. For larger systems, export limitation under G100 is often used to secure a connection quickly and avoid costly network reinforcement, capping what the array can push to the grid while leaving on-site self-consumption untouched. DNO timescales run from around 4 to 12 weeks for smaller connections up to 6 to 18 months for the largest, so we submit the G99 application early, usually before the site survey, to keep it off the critical path.

The works themselves fall under CDM 2015 on larger installs, and we notify your buildings insurer so cover continues with the correct certification in place. All of it is delivered under MCS commercial certification, with NICEIC, RECC and TrustMark registration, an IWA insurance-backed workmanship warranty, and ISO-accredited processes behind the work.

Funding routes that fit warehouses and industrial units

There is rarely a need to find six figures of capital up front. Three routes cover almost every warehouse project, and we model all three side by side with the internal rate of return for each.

• Cash purchase. You own the system outright and take the full benefit of 100 per cent Annual Investment Allowance in year one. Best when there is capital available and you want the shortest route to the highest return.
• Asset finance. The cost spreads over five to seven years and is usually cash-flow positive from month one, because the monthly finance payment is less than the bill saving it replaces. You own the system at the end.
• Power Purchase Agreement (PPA) or rent-a-roof. A funder installs and owns the array and you buy the power it generates at a fixed rate below grid, with zero capital outlay. This suits the landlord-and-tenant splits common in the sector, where neither party wants the whole capital cost on their balance sheet.

On the incentives side, the Smart Export Guarantee pays for any surplus you export, and while warehouses with strong daytime or round-the-clock demand export less than a lightly used office, a competitive SEG tariff still adds to the economics. Where a unit is part of a heavier industrial operation, it may sit alongside process load that qualifies for the Industrial Energy Transformation Fund, which is more relevant to manufacturing and factory sites. Some combined authorities also run periodic SME decarbonisation grants worth checking before you commit to a route. The full picture is on the grants and funding page.

A representative warehouse project

Consider a third-party logistics operator running a 2,800 sqm distribution unit on the edge of a Midlands industrial estate, with an annual electricity bill around £96,000 driven by high-bay lighting, forklift charging and a chilled section. The board wanted a fast payback and, given the site was leased, no large capital sum on the balance sheet.

Modelling from half-hourly data supported a 182 kW rooftop array of roughly 330 panels on non-penetrative clip-fix mounting, generating about 168,000 kWh a year. With daytime MHE charging and refrigeration running through the working day, self-consumption came out near 78 per cent, so most of the generation displaced grid units directly rather than being exported cheaply. Annual saving landed at approximately £38,000.

The system was funded on a six-year asset-finance agreement structured to be cash-flow positive from month one, with the operator buying nothing up front. Simple payback modelled at about 5.5 years. Beyond the numbers, the renewable disclosure helped the operator retain a Tier-1 retail contract that had begun asking supply-chain partners for their Scope 2 position, a reminder that on many warehouse sites the ESG case now sits alongside the financial one. Figures are representative of the sector rather than a named client.

Common questions about warehouse solar PV

Will solar panels void our roof warranty or need structural work?

Non-penetrative clip-fix mounting clamps to standing-seam and trapezoidal metal roofs without a single penetration, so on most warehouse roofs the existing warranty is preserved. We assess roof condition and remaining warranty life before design. Roofs over about 1,000 sqm usually get a structural survey to confirm they can carry the extra dead load and cope with wind uplift, and any pre-2000 roof gets an asbestos check first. If the roof is near the end of its life, it is often worth re-roofing and installing solar together.

How much roof does a warehouse solar system need?

Roughly 5 to 6 sqm of unshaded roof per kWp. A 600 to 3,000 sqm warehouse roof typically supports a 100 to 500 kW array of about 185 to 920 panels. We size from your half-hourly consumption rather than roof area alone, aiming for annual generation equal to around 60 to 85 per cent of what you use, so the array is matched to demand rather than just filling the roof.

We lease the building. Can we still install solar?

Yes, and it is common in the sector. A Power Purchase Agreement or rent-a-roof structure lets a funder own and install the array with no capital cost to either landlord or tenant, and you simply buy the power at a fixed rate below grid. Where the tenant pays the electricity bill, they usually take the saving; where the landlord installs to lift the asset, a service-charge or green-lease route shares it. We model the structure around who holds the lease and who pays for power.

Do warehouse solar panels generate enough in the UK climate?

Yes. UK commercial arrays reliably produce 900 to 1,050 kWh per kWp per year, and modern panels generate usefully in diffuse and overcast light, not only in direct sun. Output is naturally higher from April to September, which lines up with the long daylight hours of a working warehouse. Correct panel selection, roof orientation and inverter sizing matter far more to the yield than raw sunshine hours, which is why every proposal comes from a PVSyst model rather than a rule of thumb.

How long does a warehouse solar installation take?

From signed contract to a commissioned system is typically 8 to 20 weeks. The physical install on a warehouse roof is usually one to four weeks, but the critical path is almost always the DNO connection, which runs from around 4 to 12 weeks for smaller systems up to 18 months for the largest. Submitting the G99 grid application early, before the site survey, is the single biggest lever on the overall timeline, and it is the first thing we do. Related sectors with similar profiles include retail and showrooms and agricultural buildings.