Solar PV for business premises

What commercial solar PV is and why it matters for your business

Commercial solar panels convert daylight into electricity that your business uses directly, offsetting the power you would otherwise buy from the grid at 25 to 45p per kWh. For most UK businesses with a reasonable roof, solar is the single biggest lever on their energy bill and the cornerstone of any credible renewable strategy. It is low-risk, needs little space beyond a roof you already own, and generates most strongly during the working day when your demand is highest. That alignment between generation and consumption is what makes solar panels for business pay, and it is why it is usually the first capital measure for the majority of sites.

The economics are proven and bankable. A well-designed commercial solar PV system pays for itself in 5 to 8 years, then delivers 15 to 20 more years of near-free electricity under a 25-year performance warranty. Along the way it cuts your Scope 2 carbon emissions directly, which matters more every year as customers, investors and lenders ask what your business is doing about its energy and carbon. Solar alone will not touch your gas or fleet-fuel emissions, but as the foundation of a wider stack that later adds battery storage, EV charging and heat pumps, it is where almost every business should start.

This guide is independent and technology-neutral. It does not sell one box. A good adviser assesses whether solar genuinely suits the building and load profile, sizes it from actual meter data, and says plainly when a roof or a site does not stack up.

How a commercial solar PV system works

A commercial solar installation has four core parts, and understanding them helps you judge a proposal.

Panels

The panels themselves are the generating layer. Modern commercial panels are mono-crystalline silicon, mounted in an array sized to your roof and consumption. In the UK, one kilowatt-peak (kWp) of panels needs roughly 5 to 6 square metres of roof and yields around 900 to 1,050 kWh a year, even accounting for our diffuse, cloudy light. Panels carry a 25-year output warranty and degrade only slowly, so a system installed today is still producing over 85% of its original output two decades later.

Inverters

Panels generate direct current; your building and the grid run on alternating current. Inverters do the conversion. On larger commercial roofs string inverters are typical, sometimes with optimisers where shading is a factor. The inverter is the working heart of the system and the component most likely to need replacement once across the panels’ lifetime, which belongs in the whole-life costing rather than being hidden.

Mounting

Mounting secures the array to the roof. Steel-portal warehouse and factory roofs are the best canvas in commercial solar: large, unshaded, and structurally straightforward to fix to. Flat roofs use ballasted or penetrative mounting; pitched profile roofs use clamp systems. Where the roof is not suitable, ground-mount frames or a solar carport over a car park deliver the same generation on a different footprint.

Metering and monitoring

A generation meter records what the array produces, and export metering records any surplus sent back to the grid. Real-time monitoring lets you see performance live, prove the savings for your reporting, and catch any fault early. This data also feeds directly into SECR and ESG disclosures.

Sizing and economics: the numbers that decide the return

The single most important design decision is size, and it is not set by your roof area. Every system should be sized from half-hourly meter data and modelled in PVSyst, targeting a system that covers 60 to 85% of annual consumption. Oversize it and you export cheap surplus for a few pence; undersize it and you leave savings on the table.

Self-consumption is what makes the return

The figure that decides your payback is self-consumption: the share of generated power you use on site rather than export. Most commercial sites achieve 55 to 85% self-consumption, and the higher that number, the faster the payback, because every self-consumed unit is worth the 25 to 45p you did not pay the grid, while an exported unit is worth only the Smart Export Guarantee rate. A business that operates through daylight hours, a warehouse, a factory, an office, naturally self-consumes well. This is why the load shape should be modelled before a size is quoted, not after.

What it costs

Commercial solar costs roughly £600 to £1,300 per kWp installed, with the per-unit price falling as systems get larger. In practical terms:

• A 50kW office array runs around £45,000 to £60,000
• A 250kW warehouse system runs around £190,000 to £240,000
• A 1MW factory install runs around £600,000 to £750,000

Across the full range, a typical commercial solar PV project sits between £25,000 and £1.5m depending on scale, generating anywhere from 27,000 to over 1,800,000 kWh a year and saving 6 to 420 tonnes of CO2 annually.

Payback and lifetime value

Payback typically lands at 5 to 8 years. After that, the system produces for another 15 to 20 years at near-zero running cost, all under a 25-year warranty. Over the life of the array, that is two decades of electricity at a fraction of grid prices, which is why solar is usually the strongest capital project on a commercial site’s table.

Funding and grants specific to solar

The headline cost is not the net cost. Several genuine UK routes bring it down.

100% Annual Investment Allowance. Solar PV qualifies as plant and machinery, so a profitable company can deduct the full capital cost from its taxable profit, recovering roughly a quarter of the outlay through corporation tax relief. Solar is special-rate plant, so it does not qualify for Full Expensing; above the £1m AIA cap the balance attracts the 50% first-year allowance instead. This is the primary lever on owned solar.

VAT reclaim. VAT-registered businesses reclaim the VAT on the installation in the normal way, so the effective cost falls further.

Smart Export Guarantee (SEG). MCS-certified systems earn a payment, typically 4 to 15p per kWh, for surplus power exported to the grid. This matters most for sites that export at weekends or overnight, such as offices, retail and schools. A competitive SEG tariff improves the whole business case.

For a full picture of how these stack for your project, see the grants and funding page and the indicative cost breakdown. Where capital is a barrier, an on-site power purchase agreement can deliver solar at zero capex, with a funder owning the panels and you simply buying the power below grid price.

Compliance and grid connection

Commercial solar is well-established territory, and the compliance is routine when handled by a certified specialist.

Planning. Most rooftop solar is Permitted Development under Class J of Part 14 of the GPDO 2015, so no planning application is required. Listed buildings, conservation-area sites and ground-mount arrays above certain thresholds are the exceptions and do need consent.

Grid connection. Every system needs a connection agreement with your Distribution Network Operator. Smaller systems use the G98 fast-track; most commercial installs need a full G99 application. Where the local network is constrained, G100 export limiting caps how much you send back, which often secures a connection quickly and avoids expensive grid reinforcement. Timescales run from a few weeks for small connections to several months for large ones, so applications should go in early.

Structural and asbestos. Any roof over roughly 1,000 square metres gets a structural survey to confirm it can carry the array. Roofs built before 2000 get an asbestos check, because much older commercial roofing is asbestos cement and must not be drilled. These are standard pre-installation steps, not obstacles.

Certification. Commercial solar work should be MCS-certified and covered by an insurance-backed workmanship warranty, which is also what makes a system eligible for the Smart Export Guarantee.

When commercial solar suits your business, and when it does not

It is better to be told the truth up front than to be sold a system that underperforms.

Solar suits your business well when you have a large, unshaded, structurally sound roof, ground for a mounted array, or a car park for a carport; when your demand falls in daylight hours so you self-consume most of what you generate; and when you own the building or have a long enough lease, or landlord agreement, to see the payback through.

Solar is a weaker fit when your roof is heavily shaded, north-facing, structurally marginal, or close to the end of its own service life, in which case a re-roof should come first. It is also a weaker fit if your consumption is almost entirely overnight, because you would export most of the generation at a low rate rather than self-consuming it, though a battery can partly solve that. And if you are about to move premises with no way to relocate or transfer the system, the economics need a harder look. In each of these cases a good adviser says so and points to the measure that does pay on the site.

How solar fits the wider renewable stack

Solar is the foundation, but its return improves when it is designed as part of a whole. It pairs naturally with the other technologies in the stack:

• Battery storage stores daytime surplus for evening, weekend and overnight use, lifting self-consumption from 55-75% up to 80-95% and shaving expensive peak-demand charges. Solar systems are best designed battery-ready so storage can be added once there is a year of data.
• EV charging run on self-generated solar lets you charge a fleet or staff cars at a few pence per kWh instead of grid power at 25-45p, transforming the economics of electrifying transport.
• Commercial heat pumps are strongest when run on your own solar generation, and they remove the Scope 1 gas emissions that solar alone cannot touch.
• Energy management comes first in the ideal order: cutting waste means the solar array is sized to a lower, well-managed demand, so it pays back faster.

Designing these as one integrated system, rather than three or four separate installs, is what separates a bankable roadmap from a set of product sales.

How a good assessment works

A good assessment starts with the data, not a sales pitch. Pull the half-hourly meter readings, look at the roof, land and load profile, and model the right system size in PVSyst before any quote. A good proposal is fixed-price, lays out the generation, self-consumption, saving, payback and CO2 figures, and models the funding options, cash purchase, asset finance or a zero-capex PPA, side by side so the board can decide on merit. The work should be MCS-certified and insurance-backed, with the grid application, structural survey and any planning handled as part of the job. If solar is not the right first move for the site, a good adviser says so. To start, request a quote with the site details.