Solar panels for commercial property: a portfolio decision, not just an energy one
Solar panels for commercial property work hardest when you stop treating them as a utility bill fix and start treating them as an asset management decision. For owners, landlords, asset managers and REITs running mixed office and commercial portfolios, the array on the roof does three jobs at once: it cuts the running cost, it lifts the EPC band, and it protects the lettability and capital value of the building underneath it. The reason the economics hold up is timing. The hours a commercial building draws power, IT, air conditioning, ventilation and lighting running from roughly 06:00 to 18:00, are almost exactly the hours a roof generates it, so most of what the system makes is used on site where it is worth four or five times more than exported power. Across a portfolio of offices, retail units and light industrial stock, that overlap turns a row of cost centres into a row of quietly productive assets.
The driver that has moved this up the agenda for property owners is regulatory rather than financial. Minimum Energy Efficiency Standards already bar the letting of sub-standard non-domestic property, the threshold is set to rise to band C by 2027 and band B by 2030, and a building that cannot be let is a building that has lost value. Solar is one of the few measures that can move several units up a band from a single project, which is exactly why it belongs in a green-lease and MEES conversation rather than just an energy one. Add the ESG questions that flow down from institutional investors and FTSE tenants, and on-site generation becomes the cleanest Scope 2 reduction available to defend both the income and the valuation of the holding.
How we size systems across a mixed portfolio
Sizing is driven by your half-hourly meter data and the genuine shape of each building's day, never by filling a roof. The rule we work to is to target annual generation at around 60 to 80% of current consumption, which keeps self-consumption high (typically 55 to 75% without a battery) rather than leaving you exporting cheaply. Typical office systems land in the 30 to 150 kW range, generating 27,000 to 138,000 kWh a year; light industrial units sit at 50 to 250 kW on the broad steel-portal roofs that suit clip-fix mounting, generating 46,000 to 230,000 kWh; and mixed-use buildings run 40 to 200 kW across a shared roof. Battery storage rarely pays below 100 kW, but for assets with meaningful night or weekend baseload we model it, and every system we design is built to be battery-retrofittable so the door stays open.
Costs, payback and tax relief
Across the portfolio, projects run from roughly £20,000 for a small office to £225,000 for a large light industrial unit, with cost per kW typically £900 to £1,300 below 100 kW and falling toward £750 to £950 per kW above 200 kW, so larger roofs buy cheaper generation. Simple payback sits at 5 to 8 years for most buildings, with daytime-heavy, high-baseload units at the faster end and office-only stock with quiet weekends a little longer. The biggest lever is tax: solar PV qualifies as plant and machinery, so the 100% Annual Investment Allowance lets a profitable company write off the full cost against profit in year one, an illustrative saving of around a quarter of the project value for a limited company against current corporation tax rates. On an £80,000 install that is roughly £20,000 of relief and a net cost near £60,000. First Year Allowance and capital allowance treatment vary by entity and structure, so these figures are illustrative and our finance team confirms the right route with your accountant. Our cost guide sets out worked numbers by building size.
Funding routes
Most owners we work with do not pay capex up front. The 100% Annual Investment Allowance is the foundation, expensing the qualifying plant the landlord owns in year one. On top of that, asset finance over five to seven years is usually cash-flow positive from month one, because the finance payment is smaller than the bill it replaces, and the asset is owned outright at the end. Regional support can also apply: several combined authorities, including Greater Manchester, the West Midlands, West Yorkshire and Liverpool City Region, have run SME decarbonisation grant rounds worth roughly £5,000 to £50,000, and the British Business Bank Recovery Loan and Growth Guarantee scheme can fund renewables from £25,000 upwards with a government-backed guarantee. The Smart Export Guarantee pays for surplus at rates in the 4 to 15p per kWh range, which matters for offices that empty at weekends and export 25 to 45% of generation. Where you would rather carry no capital risk, a power purchase agreement lets a funder own the array while you buy its output below grid price. The grant landscape moves, so we confirm what is live in your region at build time. See the full picture on our grants and funding page.
Compliance, leases and sector considerations
For a portfolio owner, the lease and metering structure usually needs more thought than the planning. Most offices and industrial units fall under Permitted Development as Class A Part 14 of the GPDO, so a standard rooftop array needs no application, though high street retail in a conservation area can require planning permission and a listed building always needs Listed Building Consent. On multi-let and mixed-use buildings, multiple meters complicate self-consumption, so an allocation model such as a sleeve PPA or virtual net metering is the route, with cost recovery via service charge under the RICS Code on Service Charges 2018 and a green-lease addendum to share the benefit cleanly. Any building from before 2000 needs an Asbestos Management Survey before work begins, the post-install EPC records the rating uplift (often a band D to a C or a C to a B) against the asset, and we notify your insurer with the certification they need. We are MCS certified for commercial work, NICEIC registered, and RECC and TrustMark licensed, so the install satisfies both your insurer and a future buyer's surveyor.
How we approach the project
We model every building from its half-hourly meter data rather than a generic per-square-metre estimate, because the gap between an optimistic guess and the real load curve is where disappointing solar projects come from. We size for self-consumption first, check the roof build-up and any asbestos before we quote, and back every generation and payback claim with PVSyst modelling that we share with you. Below 100 kW we submit the faster G98 grid application early (a four to eight week DNO timescale); above 100 kW we start the G99 application alongside the survey, since the connection is the long pole. From contract to a commissioned system is typically eight to sixteen weeks, with the physical install one to four weeks. You receive a fixed-price proposal, a clean handover pack for your accountant, and a 10-year insurance-backed workmanship warranty behind the install.
An illustrative example
As an illustrative composite based on typical projects: an asset manager held a building let to a professional services firm paying around £18,000 a year for power, and installed roughly 75 kW across the roof, about 138 panels with a single inverter, generating in the region of 68,000 kWh a year. The project was funded by asset finance over six years and was cash-flow positive from month one, the EPC uplift supported the building's lettable value at the next rent review, and a lobby display showed live generation to visiting tenants. The payback worked out close to 6.5 years. These figures are illustrative only and depend on the specific site, roof, load profile, tariff and lease.
To dig into specific building types across your portfolio, see our pages on solar panels for offices and mixed-use commercial buildings. When you are ready, work through the cost guide, check the grants and funding routes, read the commercial solar FAQs, or request a free feasibility from your meter data and roof drawings.
