Commercial Solar Panels UK: Costs, ROI and How Business Solar Works

Solar panels for homes get most of the headlines, but commercial solar panels in the UK often deliver an even stronger financial case. Daytime businesses use electricity exactly when the sun is generating it — meaning self-consumption rates of 70–90% are realistic, versus 30–40% for a typical household. Add the Annual Investment Allowance, a landmark business rates exemption and falling installation costs, and it's no surprise that more UK businesses are treating rooftop solar as a capital investment rather than a green gesture. This guide explains how commercial solar panels work, what they cost, and how the numbers stack up for an SME owner or finance director.

Commercial vs residential solar: key differences

Scale, voltage and grid rules all differ. A domestic system is typically 4–12 kWp and connects to the grid under the simplified G98 notification route. A commercial system for a warehouse, office block or retail unit usually starts at 20 kWp and can run to 500 kWp or beyond. Systems above 50 kWp require a full G99 application to the Distribution Network Operator (DNO) — a process that can take three to six months and requires detailed electrical design work before approval. Larger commercial systems also commonly use three-phase power, which allows them to supply the building's heavier machinery and HVAC loads directly. For a full breakdown of the notification process, see our G98 solar notification guide.

Planning permission is another point of difference. Most rooftop commercial solar installations qualify as permitted development in England, but listed buildings, conservation areas and systems that significantly alter the roofline may require a full application. Our article on solar panel planning permission covers the rules in detail.

How much do commercial solar panels cost in the UK?

Installed costs fall sharply as system size increases. For a small business system in the 20–50 kWp range, expect roughly £1,000–£1,200 per kWp installed — partly because mobilisation, scaffolding and DNO connection fees are spread over fewer panels. Larger systems above 100 kWp typically come in at £600–£900 per kWp. As a rough guide:

• 20 kWp (small office or shop) — around £20,000–£25,000
• 50 kWp (mid-size commercial unit) — around £40,000–£55,000
• 100 kWp (warehouse or factory) — around £65,000–£90,000
• 250 kWp+ (large industrial) — £150,000–£200,000+

Prices vary by roof type (flat roofs need ballasted racking, adding cost), location and the specific inverter and panel brand specified. Always obtain at least three quotes from MCS-accredited installers.

Return on investment and payback period

A typical commercial system pays back in four to seven years, after which it generates essentially free electricity for the remainder of its 25–30 year life. The payback depends on three variables: how much electricity the business consumes during the day, the local grid import price (currently 24–30p/kWh for many commercial tariffs), and whether the system is self-funded or financed.

A profitable business that claims the Annual Investment Allowance (see below) can knock one to two years off that payback figure, because the tax relief effectively reduces the net cost of the installation by 25% in year one. A business importing electricity at 28p/kWh and self-consuming 80% of output from a well-sized system can realistically see annual savings of £8,000–£12,000 per 50 kWp installed.

Tax reliefs: Annual Investment Allowance and business rates

The Annual Investment Allowance (AIA) is one of the most compelling reasons to invest in commercial solar now. The AIA limit is permanently set at £1,000,000 per accounting year, meaning most SMEs can write off the entire cost of a solar installation against taxable profits in the year of purchase. At the current 25% corporation tax rate, a £100,000 installation generates £25,000 of corporation tax relief immediately, reducing the effective net cost to £75,000. For investments above the £1M AIA cap, a 50% First-Year Allowance applies to the remainder.

Business rates exemption. A government policy introduced in April 2023 provides a 100% business rates exemption for new rooftop solar installations until 2035. This means adding solar panels to a commercial property does not increase its rateable value — removing a deterrent that previously made large rooftop arrays financially risky. The exemption covers rooftop arrays, solar carports and on-site battery storage.

VAT note. Unlike domestic installations (which attract 0% VAT), commercial solar is subject to the standard 20% VAT rate. However, VAT-registered businesses can reclaim this as input tax in the normal way, provided the solar system is used for taxable business activities, so the net VAT impact is typically neutral for VAT-registered companies.

Finance options: buying, asset finance and PPAs

Outright purchase gives the best long-term return and lets the business claim the full AIA benefit in year one. It requires upfront capital but is often cash-flow positive within five years.

Asset finance (hire purchase or a solar loan) spreads the cost over three to seven years. Many commercial solar finance packages are structured so that monthly energy savings — plus the reduced tax bill — exceed the finance repayment from day one, making the project self-funding from the outset.

Power Purchase Agreements (PPAs) require zero upfront capital. A third-party developer funds, installs and owns the array on your roof; you simply buy the electricity it generates at a fixed rate (typically 15–25% below your current grid tariff) under a 15–25 year contract. PPAs are especially attractive for businesses with limited capital budgets or those that want to avoid balance-sheet debt. The trade-off is that you do not own the asset and cannot claim the AIA. Export income also accrues to the developer rather than the business.

Exporting surplus electricity: SEG vs PPAs

If you own the system and generate more power than the business uses, you can export the surplus and earn via the Smart Export Guarantee (SEG). Ofgem's SEG obliges larger energy suppliers to pay a per-unit export rate; commercial installations up to 5 MWp are eligible provided they hold MCS certification and have a smart meter. Export rates in 2026 vary between roughly 4p and 15p per kWh depending on the tariff, though businesses with high daytime consumption typically export little and maximise value through self-consumption. For rate comparisons, see our Smart Export Guarantee 2026 guide.

Under a PPA, the developer typically retains SEG rights. Some contracts share a portion of export revenue with the building owner — always check the contract terms.

Grid connection: G98 vs G99

Systems up to 50 kWp can connect under the G98 simplified notification: you (or your installer) notify the DNO and, subject to no objections, can energise the system within 20 working days. Systems above 50 kWp require a G99 application, which involves a detailed technical review and may require network reinforcement if local grid capacity is constrained. G99 approvals can take three to six months, so factor this into your project timeline. Your installer should manage the DNO application as part of the installation contract.

Finding a commercial solar installer

Always use an MCS-accredited installer for commercial projects. MCS (Microgeneration Certification Scheme) accreditation is required to qualify for the SEG and is a condition of most commercial solar finance packages and building warranties. Commercial installers should also carry Public Liability Insurance of at least £5 million and be able to provide references from similar-scale projects.

When requesting quotes, ask each installer to provide: a detailed shading analysis using software such as PVsyst or PVGIS, a roof structural survey (essential for flat roofs and older buildings), a half-hourly meter analysis to size the system against your actual consumption profile, and a projected energy yield model.

For guidance on vetting installers — including questions to ask and red flags to watch for — see our article on how to choose a solar installer in the UK.

Is commercial solar right for your business?

The strongest candidates are businesses that occupy a building they own or have a long lease on (10+ years), have a significant daytime electricity load (manufacturing, refrigeration, offices with air conditioning), are profitable enough to benefit from the AIA, and have a roof in reasonable condition with good south or south-west facing sections. Businesses that rent short-term, have heavily shaded roofs, or operate mainly at night will see a weaker case — though a PPA may still make sense where the landlord's co-operation can be secured.

The combination of a 4–7 year payback, 100% AIA tax relief, a 10-year business rates exemption and 25–30 years of low-cost electricity makes commercial solar one of the strongest capital investments available to UK businesses in 2026.