Most pages that answer this question give a single number with no source. This one uses the Department for Energy Security and Net Zero’s cost data, which records the total installed cost of every MCS-certified solar system in the country by region and size, and then explains what sits behind the regional average so you can read your own quote against it.
The official figures for the West Midlands
DESNZ analysed 21,961 West Midlands installations in the 2025/26 financial year. The mean cost across all of them was £1,700 per kW. By size band, the figures that matter for a business roof are £1,628 per kW for 4 to 10 kW systems (7,161 installs) and £1,233 per kW for 10 to 50 kW systems (1,181 installs). Nationally, the medians were £1,546 per kW for 4 to 10 kW and £1,204 per kW for 10 to 50 kW.
Above 50 kW DESNZ does not publish a band, because the number of installs is small and the jobs vary too much to average. For a 100 kWp or 250 kWp system the honest statement is that cost per kW continues to fall with size, and that the price is set by the roof and the grid connection as much as by the panels.
What the per-kW figure hides
Three things explain most of the spread between one quote and another at the same system size.
Fixed costs. Scaffolding or mobile access, the structural report, the G99 application, the monitoring platform and commissioning cost about the same on 30 kWp as on 150 kWp. That is why the 10 to 50 kW band is £400 per kW cheaper than the 4 to 10 kW band, and why an array sized to the roof rather than to a round number is usually the better buy.
The roof. A profiled steel deck on a modern industrial unit, with a clear span and simple access, is the cheapest roof in the country to install on. A single-ply membrane needs ballasted, non-penetrating mounting to protect the membrane warranty, which shifts the question to imposed load and wind uplift. An older building may need structural strengthening before it can carry an array at all. We survey the structure before we quote, not after.
The grid connection. Any system above 3.68 kW per phase needs a G99 application to the network operator, and on larger systems the operator may impose an export limit or ask for a connection upgrade. Birmingham sits on National Grid Electricity Distribution’s East Midlands licence area, which surprises people; the Black Country is on the West Midlands area. The application is the slowest part of any project, and it is in our fixed price.
The price it is competing with
A solar system is bought to displace grid electricity, so the right comparator is what your business pays per kWh. DESNZ’s quarterly energy prices put the average non-domestic price in the first quarter of 2026 at 24.14p per kWh including the Climate Change Levy, across all consumption bands, with the smallest users paying the most. The Climate Change Levy itself is £0.00801 per kWh from 1 April 2026, rising to £0.00827 from 1 April 2027, and electricity you generate and use behind your own meter does not attract it.
Two more levers change the arithmetic. In England, renewable generation and storage plant, the panels, inverters and batteries, is left out of a building’s rateable value from 1 April 2022 until 31 March 2035, so a rooftop array should not raise your business rates bill, although on larger systems the supports and settings can still be valued. And the capital cost qualifies for capital allowances: the Annual Investment Allowance at 100% in year one up to £1m, available to companies and unincorporated businesses alike, or above that the 50% first-year allowance for companies. Solar is special-rate plant, so it is excluded from full expensing, whatever a brochure says; our capital allowances guide sets out the routes.
A worked example: 100 kWp on a Birmingham roof
Take a 100 kWp array on an industrial unit. At the West Midlands 10 to 50 kW mean of £1,233 per kW it would cost about £123,300 as an average job; a larger system on a good roof should come in below that figure, and we would rather you held us to the quote than to a statistic.
PVGIS, the European Commission’s yield model, puts a south-facing 4 kWp array in Birmingham at 3,864 kWh a year, which is 966 kWh per kWp. A 100 kWp array therefore generates roughly 96,600 kWh a year. If the business uses 70% of that on site, 67,620 kWh, it displaces electricity at 24.14p and saves about £16,300 a year; the remaining 28,980 kWh exported at a business export rate of around 12p adds £3,500. On those inputs the system returns its cost in a little over six years before tax relief, and faster after the Annual Investment Allowance. A manufacturer using 90% on site does considerably better; an office exporting half does worse. The self-consumption share is the number that matters, which is why every proposal starts with your half-hourly data.
What to ask any installer
Whether the structural survey and G99 are in the price. Which roof mounting system and why. What the generation forecast is based on, and whether it is matched to your consumption profile rather than to the roof. Whether the panels and inverter carry the warranties claimed. And who does the aftercare. Our page on commercial solar panels Birmingham sets out how we answer each of those, and the West Midlands page covers the wider region.
Sources
- DESNZ, Solar PV cost data, 2025/26 Total Installed Cost workbook, “Regional costs (TIC)” and “Annual table (TIC)” sheets: gov.uk/government/statistics/solar-pv-cost-data
- DESNZ, Quarterly energy prices, table 3.4.2, non-domestic electricity prices including CCL, Q1 2026: gov.uk/government/statistical-data-sets/gas-and-electricity-prices-in-the-non-domestic-sector
- Climate Change Levy rates from 1 April 2026 and 1 April 2027: gov.uk/guidance/climate-change-levy-rates
- Renewable plant and machinery excluded from rateable value, 1 April 2022 to 31 March 2035 (England): The Valuation for Rating (Plant and Machinery) (England) (Amendment) Regulations 2022, S.I. 2022/405
- Full expensing and the 50% first-year allowance, special-rate assets including solar panels: gov.uk/guidance/check-if-you-can-claim-full-expensing-or-50-first-year-allowances
- Yield: European Commission JRC, PVGIS 5.3, Birmingham, 4 kWp south-facing at 35 degrees, 14% system loss: re.jrc.ec.europa.eu/pvg_tools/en/
- G98 and G99 thresholds: Energy Networks Association, engineering documents