Solar Panels for Commercial Buildings: Which Roofs Suit PV?

Which commercial roofs actually suit solar?

Solar panels for commercial buildings work on far more roof types than most business owners expect. The question is rarely whether a roof can carry PV. It is whether the array will pay back, how much it will cost to mount, and whether the roof has enough life left to justify the install. Roof shape is only part of that picture.

The single best canvas for commercial PV in the UK is a large, unshaded steel-portal warehouse or industrial roof. Flat retail and supermarket roofs are next. South-facing pitched roofs on offices, barns and older commercial premises work well too. Even east-west and shallow-pitch roofs are viable, they just generate a slightly flatter, wider production curve rather than a sharp midday peak.

This guide walks through each common commercial roof type, the structural and shading factors that decide feasibility, and when ground-mount or a solar carport beats rooftop. Where you want firm numbers for your own building, our cost guide breaks down real per-kWp pricing across the 30 kW to 1 MW range, and you can request a free desk feasibility modelled from your half-hourly meter data.

The four commercial roof types, ranked

Not all roofs are equal, but almost all are workable. Here is how the main commercial roof types compare for solar PV.

Roof type	Typical buildings	Mounting method	Suitability	Notes
Steel-portal metal (trapezoidal / standing seam)	Warehouses, industrial units, modern factories	Non-penetrative clip-fix	Excellent	Large, unshaded, preserves the roof warranty
Flat (felt, single-ply membrane)	Retail parks, supermarkets, offices	Ballasted or fixed frames at 10 to 15 degrees	Very good	Panels tilted and spaced to avoid self-shading
Pitched, south-facing (slate, tile, sheet)	Offices, agricultural barns, older premises	Fixed rail mount	Very good	Best generation when close to south at 30 to 40 degrees
Pitched, east-west	Any pitched roof running the wrong way	Split-array rail mount	Good	Flatter, wider production curve, still strong self-consumption

The reason warehouse roofs top the list is simple. They are big, they are usually flat-planed steel with no dormers or plant to shade the array, and clip-fix mounting fixes to the seams or crowns without a single roof penetration. That keeps the roof watertight and, crucially, preserves the manufacturer’s roof warranty. A 1,000 sqm warehouse roof typically supports 150 to 180 kWp of PV.

Flat roofs need a little more thought. Panels sit on ballasted or mechanically-fixed frames tilted to around 10 to 15 degrees, and rows are spaced so one does not shade the next. That spacing means a flat roof yields a bit less per square metre than a pitched roof, but the trade is usually worth it given how much flat roof commercial buildings tend to have.

What actually decides feasibility

Roof shape gets the headlines. These five factors decide whether the project goes ahead.

1. Structural loading

PV adds dead load and, more importantly, wind uplift. Modern panels and framing are light, but the array still has to be signed off against the roof’s capacity. As a rule, roofs over about 1,000 sqm get a structural survey for the additional dead load and wind uplift before design is finalised. Older buildings, snow-loading regions and roofs already carrying plant need particular attention. This is engineering, not a formality, and it is one of the reasons a specialist beats a general contractor.

2. Remaining roof life

There is no sense fixing a 25-year asset to a roof with five years left in it. We assess roof condition and remaining warranty life before anything else. If the roof needs replacing inside the panels’ working life, the sensible move is to re-roof first, or fold a re-roof into the project. Buildings constructed before 2000 also need an asbestos management survey, since fibre-cement and older sheeting can contain asbestos that must be handled correctly.

3. Shading and orientation

Chimneys, parapets, rooftop plant, neighbouring buildings and trees all cast shade, and shade on even one panel can drag down a whole string unless the system is designed around it. Orientation matters too, though less than people think. A south-facing pitch at 30 to 40 degrees is the textbook optimum, but east-west arrays and shallow pitches still perform well and often align better with all-day commercial demand.

4. Daytime demand

This is the factor that competitor sites barely mention, and it matters more than roof shape. A commercial PV system is only as good as the share of its output you use on site. A building occupied 09:00 to 18:00 typically self-consumes 55 to 75 percent of its solar without a battery. High, steady daytime load, think refrigeration, forklift charging, process lines, pushes that past 80 percent. That is why factories and cold-storage warehouses reach 4 to 6 year paybacks while lighter-use offices sit nearer 7. Our savings calculator lets you model your own self-consumption.

5. Grid connection

Any commercial system above roughly 50 kW needs a full G99 application to your Distribution Network Operator. For larger arrays, export limitation (G100) is often used to secure a connection quickly and avoid costly network reinforcement. Timescales run 4 to 12 weeks for smaller connections and 6 to 18 months for the largest, so the DNO application goes in early, usually before the site survey.

When the roof is not the answer: ground-mount and carports

Sometimes the roof is too small, too shaded, too weak, or too close to end of life. That does not kill the project. It changes the mounting.

Option	Best for	Cost per kWp	Trade-off
Rooftop PV	Buildings with sound, unshaded roofs and enough area	Lowest, £600 to £1,300 per kWp by size	No land used, but limited by roof condition and area
Ground-mount	Sites with spare land and roof shortfall	Slightly higher (groundworks, fencing)	Needs land and often full planning above PD thresholds
Solar carport	Sites with large car parks	Highest per kWp	Adds EV charging and shaded parking, dual land use

Ground-mount suits manufacturing and agricultural sites where roof area falls short of demand but there is spare land. It costs a little more per kWp because of groundworks and fencing, and arrays above permitted-development thresholds need a full planning application. Solar carports are the priciest per kWp but earn their keep where a large car park can double as a generation asset, particularly when paired with EV charging. Roof, ground and carport can all be combined on a single site where one alone cannot meet demand.

PV only, or PV plus battery?

The other question that shapes a commercial install is storage. A battery is not automatic. It earns its place when a meaningful share of demand falls outside generation hours.

Configuration	Self-consumption	Effect on savings	Best for
PV only	55 to 75 percent	Baseline	09:00 to 18:00 offices, warehouses, schools
PV plus battery	80 to 95 percent	Adds 25 to 40 percent to annual savings	Hotels, restaurants, sites with evening, weekend or overnight load

Storage typically lifts self-consumption from the 55 to 75 percent band to 80 to 95 percent, adding 25 to 40 percent to annual savings, at the cost of a longer payback. It is usually worth modelling above 100 kWp, or wherever evening, weekend or overnight baseload is significant. Hospitality and refrigeration-heavy retail are the classic candidates. We model PV-only and PV-plus-battery side by side and design every system to be battery-ready even if you add storage later. Your building type is a strong steer here, and our sector pages for warehouses and industrial units and hospitality and leisure go into the load profiles in detail.

Sizing from demand, not roof area

A common mistake is to fill the roof with panels because the space is there. Commercial PV is sized from your annual energy spend and half-hourly consumption shape, not roof area alone. The design target is usually annual generation equal to 60 to 85 percent of current consumption, which maximises self-consumption while avoiding excessive low-value export.

The rule of thumb: 1 kWp of PV occupies roughly 5 to 6 sqm of roof and generates about 900 to 1,000 kWh a year in the UK. A 250 sqm office roof supports around 30 to 40 kWp. A 1,000 sqm warehouse roof supports 150 to 180 kWp. But whether you should install that much depends entirely on what you consume during daylight hours. Oversize the array against a light daytime load and you export a lot of power at the modest Smart Export Guarantee rate of roughly 4p to 15p per kWh rather than displacing grid electricity at 25p to 45p.

The numbers that make it stack up

Whatever the roof, the economics of solar panels for commercial buildings rest on the same levers.

Commercial PV typically costs £900 to £1,300 per kWp for systems under 100 kW, falling to £750 to £950 per kWp between 100 and 250 kW, and £600 to £800 per kWp above 500 kW. In real terms a 50 kW office system is roughly £45,000 to £60,000, and a 250 kW warehouse system £190,000 to £240,000.

Two tax levers change the headline price. 100% Annual Investment Allowance lets a profitable limited company deduct the full capex from taxable profit in year one, an effective saving of around a quarter of the price. And commercial VAT is reclaimable for VAT-registered businesses, it is not zero-rated (that relief is domestic only). Add the Smart Export Guarantee for surplus, and typical commercial payback lands at 5 to 8 years, against a 25-year panel performance warranty. That is 15 to 20 years of near-free power once the system has paid for itself. For the full breakdown of reliefs and grants, see our grants and funding routes, and for common queries our FAQs cover connection, planning and finance.

So, which roofs suit PV?

Almost all of them. If your building has a sound roof with reasonable orientation, no severe shading, and daytime electricity demand, it is a candidate for commercial solar PV. The best-suited are large, unshaded metal warehouse and industrial roofs, followed by flat retail roofs and south-facing pitched roofs. Weak, shaded or ageing roofs are not dead ends, they point toward ground-mount, carports, or a re-roof first.

The honest answer for any specific building comes from the survey and the model, not a rule of thumb. We assess roof condition, structural loading, shading and your half-hourly demand, then tell you plainly whether solar suits your site. Where it does, you get a fixed-price proposal backed by a shared yield model. Request your free desk feasibility and we will tell you what your roof can do.