250kW commercial solar — cost, ROI & payback

At 250kWp, commercial solar sits at the large-scale end of the market, where fixed costs - design, scaffolding, the DNO application, commissioning - spread across more capacity and push the price per kWp down. Industry pricing for systems at this scale in 2026 runs roughly £700 to £850 per kWp, giving an installed range of about £175,000 to £212,500 before VAT³. A reasonable planning figure for a straightforward roof-mounted array is around £190,000 (about £760 per kWp).

This is an estimate for a typical site. Your quoted price will move with panel and inverter choice, roof type (a standing-seam metal roof is cheaper to fix than an old asbestos or fragile roof), whether you need a new transformer or grid reinforcement, and how much your Distribution Network Operator (DNO) allows you to export. A 250kW system needs a G99 connection application and DNO approval, and some sites are given an export limit that shapes the design.

The table below shows where the money goes on a typical £190,000 roof-mounted 250kW installation. Proportions vary by installer and site, so treat this as an illustrative split rather than a fixed quote.

Commercial solar pays 20% VAT, not the 0% rate that applies to domestic installations - a VAT-registered business normally reclaims it¹. Battery storage is a common add-on that is priced separately and lifts self-consumption on sites with an evening or weekend load.

UK commercial arrays yield roughly 950 kWh per kWp per year in typical conditions, so a 250kW system generates around 237,500 kWh annually. Actual output depends on your location, roof pitch and orientation, and shading - a south-facing roof in the South West will out-generate a shaded north London site.

What matters financially is not total generation but self-consumption - the share you use on site instead of exporting. Every kWh you self-consume avoids buying grid electricity at the full commercial rate; every kWh you export earns a much lower price. Commercial self-consumption typically runs 60% to 85% depending on sector and shift pattern: a factory or cold store running all day sits at the top of that range, while a site that is quiet at weekends sits lower. A warehouse with mostly daytime forklift charging and lighting might land around 65-75%.

For the figures below we assume a 65% self-consumption base case, which is deliberately conservative for a large array. If your load is heavier in daylight hours - or you add storage - your savings rise. Sector-specific patterns are covered on our warehouse, factory, farm, school, retail and hotel pages.

The table below models a typical 250kW site. It uses a commercial electricity price of 24p per kWh - in line with the DESNZ non-domestic average of about 24.14p per kWh (including the Climate Change Levy) for early 2026⁴ - and an export price of 4.5p per kWh, broadly consistent with Smart Export Guarantee and commercial export tariffs⁵.

On an installed cost of £190,000, a net annual benefit of about £39,000 gives a simple payback of roughly 4.9 years. After the year-one 50% first-year allowance (see below), the effective cost for a company falls to around £166,000, shortening payback to about 4.3 years. If your electricity price is higher than 24p, or your self-consumption above 65%, payback is faster; a lower price or more export pushes it out. These are estimates for a typical site.

Two tax points shape the real cost, and both are worth confirming with your accountant.

• VAT is 20%, and normally reclaimable. The 0% VAT rate applies to domestic solar only. Commercial solar pays 20% VAT, which a VAT-registered business generally recovers through its VAT return¹.
• Solar PV qualifies for the 50% first-year allowance. Solar is classed as special-rate plant, so it does not qualify for 100% full expensing (which is main-rate only) or the new 40% first-year allowance introduced from 2026 (also main-rate only). Instead, a company can claim a 50% first-year allowance on the cost, with the remaining balance written down at 6% a year in the special rate pool².

On a £190,000 system, the 50% first-year allowance lets a company deduct £95,000 from taxable profits in year one. At the 25% main rate of corporation tax that is a first-year tax saving of about £23,750, with the remaining £95,000 written down at 6% in later years. Separately, the Annual Investment Allowance can allow 100% relief on qualifying plant up to £1,000,000 in the year - which for a system of this size may cover the full cost. Which relief applies depends on your business structure and profits, so let your accountant confirm the treatment for your circumstances.

Quality solar panels are typically warranted for 25 years or more and degrade slowly - on the order of 0.5% a year. Over a 25-year life, a 250kW system generates roughly 5.4 million kWh after allowing for degradation.

Holding electricity prices flat at today's level (a deliberately cautious assumption - most forecasts expect them to rise), a net annual benefit near £39,000 accumulates to an estimated £850,000 to £900,000 before the initial outlay across 25 years. After deducting the £190,000 cost and allowing for a likely inverter replacement around years 12 to 15, the estimated net lifetime gain is on the order of £650,000 to £700,000 - roughly 3.5 to 4 times the installed cost. Independent market modelling for systems at this scale points to a 25-year internal rate of return in the mid-teens percent³.

A 250kW array needs about 1,750 m2 of usable, unshaded roof (roughly 7 m2 per kWp) - about 19,000 sq ft, or the footprint of a mid-to-large distribution warehouse. Ground-mount or solar carports are alternatives where roof space is limited.

This size typically suits businesses with:

• A large single-storey roof, or several roofs on one site - big warehouses, distribution hubs, manufacturing plants, cold stores, food production, large agricultural buildings, big-box retail, or a hospital or large school campus.
• A substantial daytime electricity demand - annual consumption comfortably above 250,000 kWh, so that most of the 237,500 kWh generated is self-consumed. Sites with electricity bills of roughly £60,000 a year or more tend to see the strongest case at this scale.
• An electrical supply and DNO connection that can accommodate the generation, confirmed via a G99 application.

If your roof or bill is smaller, a 100kW, 50kW or 30kW system may fit better - compare all sizes from 10kW upward. If you would rather avoid the capital outlay, a Power Purchase Agreement lets a third party fund and own the system while you buy the power; weigh the trade-offs on our buy vs PPA page.