The official baseline for a 250 kW system
The Department for Energy Security and Net Zero publishes the installed cost of every solar system registered on the MCS installation database; the release of 28 May 2026 covers the 2025/26 financial year and is the only official cost series for UK solar. Its limits matter: it covers installations up to 50 kW and all building types, not farm buildings alone.
The DESNZ series covers installations registered with MCS, which stops at 50 kW, so there is no official per-kW figure for a 250 kW array: it is priced from written quotes. For scale only, the 10–50 kW non-domestic mean of £1,167.29 per kW multiplied by 250 kW is £291,800. That is arithmetic, not a price: how per-kW cost changes at larger sizes is not in the official data.
The full series, with the regional means, is on the farm solar cost guide.
How big is a 250 kW array?
250 kW is about 556 modules of 450 W. At 1.998 m² a module (1762 × 1134 mm) that is roughly 1,111 m² of roof, and at 21.0 kg a module the modules alone weigh about 11.7 tonnes. Both figures come from the Trina Vertex S+ datasheet (version TSM_EN_2023_D); racking, cables and any ballast are extra, and the roof structure has to carry the whole. How to check that is in solar panel weight and roof loading on farm buildings. An array of this size usually suits a large single-span shed or store, or several buildings on one holding.
What a 250 kW array generates
At 900 kWh per kWp a year, which sits between the PVGIS figures for Cardiff (946) and Manchester (807) on a 10° roof, a 250 kW array generates about 225,000 kWh a year. What that is worth depends on how much is used on site and what the farm pays per unit, which come from your own half-hourly data and bills, and on the export rate for the rest; no generic payback figure is given here because none can be sourced. Yields by region are in PVGIS yields for farm roofs by region.
What moves a 250 kW quote
- The roof. An asbestos cement roof is overclad or replaced before panels go on; see overclad or strip an asbestos cement farm roof and solar panels on asbestos cement farm roofs.
- The structure. The frame and purlins have to carry the added load; a structural assessment is the document to ask for.
- The electrical supply and grid connection. Three-phase supply and the G99 application to the DNO; the DNO quotes its own study and works charges. See DNO grid connection for rural farm solar.
- Access and roof safety. Platform or scaffold access, edge protection and, on fragile roofs, netting under the Work at Height Regulations 2005.
- The equipment. Module and inverter choice, set out on solar panel comparison and solar inverters for farm buildings.
- Insurance and warranty. What the insurer expects and what the warranties cover are on solar panel insurance and solar panel warranty.
Tax and finance
Qualifying plant and machinery can be written off in the year of purchase under the Annual Investment Allowance (£1 million a year), so the first-year relief is the company’s marginal corporation tax rate multiplied by the qualifying cost. Asset finance and power purchase agreements are the other usual routes. The reliefs and open schemes are set out on grants and funding.
What to ask for before accepting a price
A written proposal that names the module and inverter models, the racking and who has assessed the structure; the price basis and what is excluded; the grid connection route and who pays the DNO; the roof survey result, including asbestos; the warranty terms; and a programme that names its dependencies. Other sizes: 50 kW · 100 kW · 500 kW.
Common questions
How much does a 250 kW farm solar install cost?
There is no official per-kW figure above 50 kW: the DESNZ series stops at the MCS limit. A 250 kW array is priced from written quotes. For scale only, the 10–50 kW non-domestic mean of £1,167.29 per kW multiplied by 250 kW is about £291,800; it is arithmetic on a smaller band, not a price.
How many solar panels does a 250 kW system need?
About 556 modules of 450 W, which covers roughly 1,111 m² of roof; module weight alone is about 11.7 tonnes at 21.0 kg a module (Trina Vertex S+ datasheet, 1762 x 1134 mm). Racking and cables add to that, and the roof structure has to carry it.
How much will a 250 kW system generate?
About 225,000 kWh a year at 900 kWh per kWp, a figure that sits between the PVGIS results for Cardiff (946) and Manchester (807) on a 10° roof. Orientation, shading and location move it; the yield guide gives figures by region.
Can I finance a farm solar install?
Capital purchase, asset finance and power purchase agreements are the usual routes; which suits depends on the farm’s capital and tax position. The Annual Investment Allowance gives first-year relief on qualifying plant and machinery, worth the company’s marginal corporation tax rate on the cost in the year of installation. The finance and tax pages set out the detail.