The short answer
A 250 kWp commercial solar system costs £190,000–£230,000 installed in the UK and generates around 237,500 kWh a year (about 950 kWh per kWp). It needs roughly 1,500 m² of clear roof — factory or mid-size warehouse scale — and at high daytime self-consumption can pay back in 2–5 years.
A 250 kWp system is a serious commercial array — the scale of a factory or a mid-size warehouse roof. It is large enough to cover a substantial share of an industrial electricity bill, and at this size the cost per kWp is much lower than for a small SME system. It also crosses into a different planning and grid regime: above 50 kW, prior approval from the local authority can apply, and the grid connection is a full application rather than a simple notification. This page sets out the numbers for this size specifically. For a figure tailored to your roof, the calculator takes about a minute.
Who needs a 250kW system?
Size a solar system to your daytime electricity use, not to how much roof you have. A 250 kWp system fits a business with a large, steady demand through the working day — a factory running production lines, a mid-size warehouse with refrigeration or automation, or a distribution operation. The closer your usage pattern is to the solar generation curve, the more of the output you self-consume, and self-consumed power is what makes the economics work at this scale.
Match the array to demand, not just the roof
A big roof can host a big array, but generation that you export earns far less than the power you use on site. The strongest 250 kWp cases are operations that draw most of the output during daylight. Use the calculator for a number based on your own roof and bill.
This is roughly warehouse and factory scale, so the suitability and roof-economics detail is covered on our warehouse solar installers guide. The general principles of sizing a commercial system are on our guide to solar for business.
What does a 250kW system cost?
A 250 kWp system costs £190,000–£230,000 fully installed in 2026 — roughly £750–£950 per kWp at this scale. That price includes the panels, inverters, mounting system, scaffolding or access, design and the grid connection work. The table puts it alongside the sizes either side, so you can see how the cost per kWp keeps falling as systems get bigger.
| System size | Typical installed cost | Approx. per kWp |
|---|---|---|
| 50 kWp | £63,900–£70,000 | £1,278–£1,500 |
| 250 kWp | £190,000–£230,000 | £750–£950 |
| 500 kWp | £375,000–£425,000 | £750–£850 |
The full breakdown of what sits inside a commercial solar price — hardware, labour, scaffolding, grid fees and survey — is on our commercial solar cost guide. A 250 kWp system sits above the £1m Annual Investment Allowance threshold for total spend per year in most cases too, so the year-one tax treatment is worth checking — we cover allowances on our grants and tax relief guide.
How much will a 250kW system generate?
Output depends on UK yield, which we take as a typical 950 kWh per kWp per year — a fair mid-point for a commercial rooftop in Britain. On that basis:
| Measure | Figure |
|---|---|
| System size | 250 kWp |
| Typical UK yield | ≈950 kWh per kWp per year |
| Annual generation | ≈237,500 kWh per year (250 × 950) |
| Value if all self-consumed | ≈£59,375 per year at 25p/kWh |
Yield is higher on a south-facing, unshaded roof and in the sunnier south of the country, and lower with shading or an east–west split. The savings figure above assumes every unit is used on site; in practice a business self-consumes a share of what it generates, and exported units earn far less than the 25p you avoid by using power yourself. That balance is why a daytime-heavy demand profile matters so much, and it is what decides payback — our payback and ROI guide works through it. At warehouse and factory scale, payback typically lands in the 2–5 year range.
How much roof space does a 250kW system need?
A 250 kWp array needs roughly 1,500 m² of usable roof, working on about 6 m² per kWp (250 × 6). That is the footprint of a mid-size warehouse or factory roof. On a flat roof you usually need a little more, because panels are tilted and spaced so they don't shade each other through the day. The roof also has to be structurally sound with at least ten years of life left — a structural survey (typically £500–£2,000) confirms it can carry the load before anything is fitted.
What grid approval does a 250kW system need?
A 250 kWp system is well beyond the size handled by simple notification, so it needs a full G99 connection application to your distribution network operator. At this scale the network often offers a flexible, export-limited connection — allowing the system but capping how much it can push back to the grid at busy times — which can be quicker and cheaper than a firm connection. The grid application is usually the slowest single step, so starting it early keeps the overall timeline under control.
Systems over 50 kW and prior approval
Most commercial rooftop solar is permitted development, but a system above 50 kW can require prior approval from the local planning authority before it goes ahead. Your installer normally handles both this and the grid application; our planning permission guide sets out where it applies.
Stepping up or down a size
250 kWp is one point on a range. If your roof or bill is smaller, a 50 kWp system at £63,900–£70,000 may be the better fit. If you have a larger warehouse or distribution roof, the next common step up is a 500 kWp system, where the cost per kWp falls a little further. For something between, a 100 kWp system is a different size class again — our sister site SolarGridCheck covers it in full: see their 100kW solar system guide.
Frequently asked questions
How much does a 250kW solar system cost in the UK?+
A 250 kWp commercial solar system costs roughly £190,000 to £230,000 fully installed in 2026, which works out at about £750 to £950 per kWp. At this scale the cost per kWp is far lower than for a small system, because fixed costs like design, scaffolding and the grid application are spread across far more panels.
How much electricity does a 250kW solar system generate?+
A 250 kWp system generates around 237,500 kWh a year in the UK, based on a typical yield of about 950 kWh per kWp annually. Output peaks in summer and dips in winter. On a large flat roof the array is usually laid out to make the most of the available space rather than chasing a perfect south-facing pitch.
How much roof space does a 250kW solar system need?+
A 250 kWp array needs roughly 1,500 square metres of clear, structurally sound roof, working on about 6 square metres per kWp. That is the scale of a mid-size warehouse or factory roof. On a flat roof you usually need a little more, because tilted panels are spaced to avoid shading each other through the day.
What size business does a 250kW system suit?+
A 250 kWp system suits a business with a large daytime electricity demand, such as a factory or mid-size warehouse running machinery, refrigeration or distribution operations through the working day. The economics are strongest when most of the generation is used on site. Our calculator sizes the system to your actual roof and bill.
Does a 250kW solar system need a grid connection application?+
Yes. A 250 kWp system is well above the level handled by simple notification, so it needs a full G99 connection application to your distribution network operator. At this size the network may offer a flexible, export-limited connection to manage local capacity, and a system over 50 kW can also need prior approval from the local planning authority.
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Updated June 2026 · By Taro Schenker, founder of Business Solar Check. We're independent — we don't install solar. Figures are indicative UK averages; your site survey confirms the numbers for your roof.