How much does commercial property solar cost?

Installed cost for commercial rooftop solar in 2026 typically runs £700–£1,100 per kWp, and the most important thing to understand is that the per-kWp price falls with scale — a 1 MWp array is far cheaper per unit than a 50 kWp one. For an owner, the headline capital figure is only half the picture: the return is governed by self-consumption and by the tax position, both of which we model from your actual half-hourly data rather than a rule of thumb.

Cost by system size

UK rooftop yield is around 950 kWh per kWp per year. Larger systems (250 kWp+) achieve the lowest £/kWp and the fastest payback. A worked 250 kWp ballasted rooftop recently came in at £185,000 including 0% VAT.

What drives the payback

Simple payback for commercial solar in 2026 is typically 4–8 years, shortening to 3–5 years on high-load assets that use most of their generation on site. Three things move that number. First, self-consumption: every unit used on site displaces grid power at ~24–28p/kWh, while exported surplus earns only the SEG rate (~12p), so a building that uses 70% of its generation pays back far faster than one exporting half of it. Second, your day-rate electricity price — larger half-hourly sites buying at ~20p/kWh have weaker solar economics than a smaller site paying 28–31p. Third, the tax stack: the Annual Investment Allowance and the business-rates exemption can take one to two years off the gross payback on a post-tax basis.

Cost by property type

The costs people forget

A credible proposal prices the whole job, not just the panels. The items that move a budget are: the G99 DNO grid connection (and any reinforcement or export-limitation it requires — often the real constraint on a large array); a structural roof-loading survey to BS EN 1991; scaffolding and access; and, where the roof membrane has under 15 years of life left, the sensible decision to re-roof and install solar in one project rather than pay to strip and refit later. We surface all of these up front in a fixed-price proposal, so what you sign is what you pay.

£0-capex routes

If you would rather not spend the capital, an operating lease or asset finance spreads the cost over the system's life, and a third-party-funded roof lease removes it entirely in exchange for rent plus a discounted supply to your occupier. The right route depends on your covenant, lease length and whether you want the asset and its allowances on your own balance sheet — see our funding and tax relief guide for the full picture.

What drives the cost of commercial solar

The headline rate for a commercial rooftop array sits at roughly £700 to £1,100 per kWp installed, ex-VAT, and falls as the system gets larger. That range is wide for a reason. The same nominal capacity can cost very different amounts on two buildings a mile apart, because the panels themselves are only part of the bill. On most projects the modules account for less than a third of the total. The rest is structure, electrical infrastructure, access and connection, and it is those items that move the number within the range.

Roof type and condition. A modern steel-portal industrial unit with a sound trapezoidal metal deck is the cheapest surface to work on. Panels clamp directly to the standing seam or fix through the sheet with weatherproof brackets, so labour is fast and predictable. A flat roof needs a ballasted or mechanically-fixed mounting frame that preserves the membrane warranty, which adds framework and weight. An older or asbestos roof, or one with a corroded deck, can rule out a direct fix altogether until it is remediated.

Structural survey. A BS EN 1991 structural assessment is a precondition, not an optional extra. The engineer confirms the roof can carry the additional dead and wind load of the array. If the structure is marginal, strengthening works, or a lighter panel and frame specification, feed straight back into the price. Budget for the survey up front rather than treating a weak result as a surprise.

DNO and G99 connection. Above roughly 50kW the grid connection is usually the single biggest variable and the most common cause of delay. Anything beyond small-scale export needs a G99 application to the Distribution Network Operator, and the network can require reinforcement or an export limitation device before it will consent. On a constrained part of the network a connection offer can run to five figures and take months. This is the item to investigate first, because it can reshape the whole scheme.

Scaffolding, access and roof height. A single-storey warehouse with clear yard access is cheap to reach. A multi-storey office in a town centre, a live retail site, or a roof that can only be reached over a fragile surface, all add access equipment, edge protection and out-of-hours working. Access is a genuine cost driver, not a rounding error.

Re-roof alignment. Solar should sit on a roof with at least fifteen to twenty years of life left, because taking an array off to replace the membrane underneath is expensive. If the roof is near the end of its lifecycle, the sensible move is to align the two works, and a combined re-roof and solar project changes the capital picture. Where a re-roof is already planned, adding solar at the same time is far cheaper than doing it twice.

Inverter and battery specification. Inverters from SMA, Fronius, SolarEdge, Sungrow or Huawei are replaced once over the system life, typically at ten to fifteen years, so that mid-life cost belongs in any honest appraisal. Adding battery storage lifts the capital cost materially but raises self-consumption, and self-consumption is the main driver of return. Whether a battery pays depends on the load profile, so it is a spec decision, not a default.

Worked payback examples by building type

The figures below are illustrative, ex-VAT, and use a yield of about 950 kWh per kWp per year and a blended saving that mixes self-consumed power against a bought price of roughly 24 to 28p per kWh with a modest export at SEG rates. Real numbers depend on your load profile, tariff and roof. Treat them as a shape, not a quote.

Two patterns stand out. First, payback tightens as the load grows: the big-box shed and the portfolio pay back fastest because a high, daytime, on-site demand means most of the generation is self-consumed rather than exported at a lower rate. An owner-occupier who runs machinery through the working day sits at the fast end of every range. Second, the small unit shows the widest cost band, because on a small array the fixed costs of survey, scaffolding and connection are spread over fewer kWp. Scale is your friend on price per kWp. You can size these ranges to your own building with the commercial solar calculator, and the underlying assumptions are set out on the cost page.

Cost after tax relief

The simple paybacks above ignore tax, and tax is where a commercial buyer pulls meaningfully ahead of a domestic one. A solar installation is a special-rate plant and machinery asset, which means the qualifying spend can be written off against taxable profit using the Annual Investment Allowance, currently £1m, giving 100% relief in the year of purchase. Full expensing does not apply in the same way to solar, and assets bought in order to lease are excluded, so a landlord typically uses the AIA plus a 6% writing-down allowance on any balance. Always take professional advice on your own position.

The mechanism matters because relief converts to cash at your tax rate. Take the 150kWp office array at a mid-point cost of £125,000. Claimed in full under the AIA at a 25% corporation tax rate, that spend reduces the tax bill by about £31,000. The effective net capital cost falls to roughly £94,000. Against an annual saving of, say, £26,000, the simple payback shortens from about 4.8 years to about 3.6 years. Business rates add to this: solar generating equipment is exempt from business rates until 2035, so the array does not raise the rateable value of the property over that window. Where public-sector funding routes such as Salix are available they can compress the picture further, and grant and funding routes are covered on the grants and funding page. The full mechanics of the allowance, including the landlord-versus-occupier distinction, are set out in the capital allowances guide for owners.

Financing the cost

The capital cost need not come from your own reserves, and the right route depends on who uses the roof, who pays the electricity bill, and how you value the asset on your balance sheet.

• Cash purchase. The simplest and cheapest over the life of the system. You own the array, keep every pound of saving and every capital allowance, and there is no finance margin to pay. The trade-off is the up-front outlay and the opportunity cost of that capital. For an owner-occupier with a strong daytime load and available reserves, cash usually gives the best whole-life return.
• Lease or asset finance. A commercial lease, hire purchase or an operating loan spreads the cost over the system life, often structured so the repayments sit below the energy saving from day one. That keeps the project cash-positive without a large outlay. You pay a finance margin, and the treatment of the allowances depends on the exact structure, so confirm who claims what before signing.
• Power purchase agreement. A third party funds, installs and owns the array and sells you the power it generates at an agreed unit rate, typically below grid price, for the term. There is no capital outlay and no maintenance burden, which suits landlords and occupiers who would rather not hold the asset. The trade-off is a lower long-run return than ownership, because the PPA provider takes the margin the saving would otherwise give you. A PPA also helps solve the split incentive on let property, where the tenant pays the bill but the landlord owns the roof.

None of these is universally best. Cash wins on whole-life value, a lease preserves working capital, and a PPA removes the asset from your books entirely. The decision turns on your cost of capital, your tax position and whether you occupy or let the building. The options are compared in full, with worked figures, in the commercial solar finance options guide, and you can model the effect of each on your own building using the commercial solar calculator before you take it to a lender or a PPA provider.