Structural Steel Fabrication: Solar panels for fabrication

Why structural-steel fabrication is one of the strongest solar fits of any building type

Structural-steel fabrication is, on paper and in the meter data, close to the ideal candidate for rooftop solar in the UK. The reasons are structural in both senses of the word. First, the buildings themselves: structural-steel shops occupy large clear-span sheds, typically 900 to 3,000 square metres of roof, that carry a big, unshaded, single-pitch or duo-pitch expanse of profiled metal well suited to rail-fixed PV. That gives you the best pounds-per-kilowatt-peak in the whole fabrication sector, because the fixed costs of scaffolding, DNO application and design spread across a 250 kW-plus array rather than a small one. Second, and more importantly, the electrical load. A structural-steel fabricator runs heavy welding sets, multi-head drilling and beam lines, cold saws and bandsaws, angle and plate rolls, shot-blast plant and an overhead crane, almost all of it drawing power across a single Monday-to-Friday day shift. That is the pattern solar is built for.

The economics of solar for a workshop turn almost entirely on self-consumption, meaning the share of what your array generates that you use on site rather than export. Every kilowatt-hour you consume yourself replaces grid electricity at the full commercial import rate of roughly 25 to 30p; every kilowatt-hour you export earns only the Smart Export Guarantee rate, typically 12 to 16p in 2026. A domestic roof sits empty through the working day and exports most of its midday output cheaply. A 24/7 process plant actually exports more of its solar than a day-shift shop, because its overnight load is met from the grid while its midday surplus spills out. Structural-steel fabrication sits in the sweet spot: the demand curve lands almost exactly on top of the generation curve, so 80 percent or more of everything the array makes is consumed on site at the full import rate. That is the single fact that drives the short paybacks this sub-sector sees, and it is why we lead with load, not roof area, on every design.

The daytime baseload a structural-steel shop feeds directly

What makes structural steel especially strong is that under the spiky, high-power equipment sits a large, near-constant daytime baseload that solar feeds smoothly all day. The shot-blast plant, dust and fume extraction, hydraulic power packs on the drilling and sawing lines, the beam-line conveyors and the ever-present rotary-screw compressor cycling to hold air pressure form a steady floor of demand that runs whenever the shop is open. On top of that floor, the heavy MIG and submerged-arc welding sets, the plasma bevel heads and the drill-line spindles draw their intermittent peaks. Solar meets the steady baseload continuously and the process peaks soak up the midday generation, so almost nothing is wasted. Where the kVA demand or the DUoS red-band charges are especially heavy, we model a battery alongside the array to shave the peaks, but most single-shift structural-steel shops reach a strong return on the PV alone. For sector context on how these shops are laid out and loaded, the industry reference maintained by the BCSA and Steel Construction Institute at Steel Construction Info (BCSA/SCI) is a useful benchmark.

A typical structural-steel install

A representative structural-steel fabrication install falls between 150 and 500 kW, using roughly 330 to 1,100 panels across 900 to 3,000 square metres of clear-span roof, for a typical project value of £100,000 to £330,000 and a payback around 4.5 years. Those are among the largest arrays and the fastest paybacks anywhere on this site, and the reason is the combination the sub-sector uniquely offers: a very big cheap roof over a very large daytime load.

We do not size the array to fill the roof. We size it to the load. The working method is to pull 12 months of half-hourly meter data from your supplier and model the array so that annual generation matches roughly 70 to 90 percent of your daytime consumption, capturing self-consumption at the full import rate while spilling only a little onto low-value export. As a rule of thumb, 1 kWp needs about 5 to 6 square metres of unshaded roof and generates 900 to 1,000 kWh a year in the UK, so a 2,000 square metre structural-steel roof will typically support 300 to 360 kWp, subject to the residual-load check described below. We anchor the design on the loads that run all day, the compressor, the extraction and shot-blast plant, the hydraulic power packs, and let the heavy welding and drilling peaks absorb the midday surplus. The output of that exercise is not a sales estimate; it is a model built from your own data, and we share the file so you or your accountant can stress-test it. You can see how the numbers move for your own consumption on our savings calculator, and the full breakdown of system pricing and cost-per-kWp sits on our cost page.

An illustrative costed scenario

Consider a mid-to-large structural-steel fabricator on a 2,300 square metre clear-span shed, running drilling and beam lines, cold saws, shot-blast and heavy welding on a single day shift, with a doubled electricity bill of around £150,000 a year. Twelve months of half-hourly data shows a strong, steady daytime profile. We model a 300 kW array of roughly 660 panels for an illustrative installed cost near £190,000 before tax relief. In a typical UK year that array generates about 275,000 kWh. With 83 percent self-consumption at a 27p import rate, the shop displaces around £61,000 of grid electricity in year one, and the modest export earns a few thousand pounds more under the Smart Export Guarantee. That is a simple payback close to 4.5 years, after which the array keeps cutting the bill for the remainder of its 30-plus-year life. A profitable company can claim the Annual Investment Allowance to write 100 percent of that qualifying spend against taxable profit in the year of purchase, worth up to roughly a quarter of the cost in reduced corporation tax, and the solar plant is exempt from business rates in England to 2035. These figures are illustrative, they depend on your tariff, load profile and tax position, and we always advise confirming the tax treatment with your accountant or HMRC. The routes are set out in full, with links to current guidance, on our grants and funding page.

The compliance that shapes a structural-steel array

Structural-steel fabrication carries one compliance consideration that is genuinely specific to it and which a generalist installer will miss: overhead-crane loading. Almost every structural-steel shop runs one or more electric overhead travelling (EOT) cranes on rails carried by the building frame, plus gantry beams and monorails. Those crane-rail and gantry dead loads, together with the dynamic loads the cranes impose, have already used part of the roof structure's capacity. Before we add a framed PV array, which contributes roughly 15 to 25 kg per square metre of dead load plus wind uplift, those crane loads must be deducted from the roof's residual capacity. This is not optional and it is not a formality: on heavy-lifting bays it is essential that a structural engineer signs off the residual roof-load budget before any panel goes up. We commission that structural survey at the outset and design the panel layout, and the choice between ballasted and penetrating fixings, around the frame's real remaining headroom.

The rest of the compliance picture follows the shared rules that govern any fabrication rooftop install. Structural-steel shops weld heavily, so the HSE welding-fume duty applies in full. Under Safety Bulletin STSU1-2019, all welding fume, including mild-steel fume, is now classed as a Group 1 carcinogen, so Local Exhaust Ventilation is required for all indoor welding regardless of material or duration, supplemented by respiratory protective equipment where LEV alone is insufficient under COSHH. That LEV ductwork and its fume-discharge stacks penetrate and vent through the same roof as the array, so we design the panel layout, cable routing and maintenance walkways around your existing and future extraction penetrations, and the extraction load itself becomes an obligatory daytime load the solar offsets. Because your shop already runs BS EN 1090 execution and usually CE or UKCA marking on fabricated steelwork, the discipline of documented structural sign-off is familiar territory, and we work to the same standard on the roof.

Grid connection is the other item that shapes the programme. Any inverter output above 16 A per phase, roughly 11 kW on a three-phase supply, needs a G99 application to your DNO before connecting, so a commercial structural-steel array is always G99. We check the three-phase 415 V supply headroom against your large motor, crane and welding loads, because an older shop can sit on a tired incoming supply, and we submit the G99 application on day one alongside the structural survey so the connection clock starts immediately rather than at contract. On the roof itself, the Control of Asbestos Regulations require a survey of any pre-2000 building before we fix anything, because asbestos-cement roofs cannot take rooftop PV directly, and the whole design is built to the RC62 rooftop-PV fire-safety Code of Practice, which insurers increasingly make a condition of cover. Most industrial rooftop PV is Permitted Development under Class A Part 14 of the GPDO, and the previous 1 MW cap was removed in December 2023, so even a large structural-steel array usually needs no planning application, subject to the projection limits and the exceptions for listed and conservation-area sites.

An illustrative case scenario

To make this concrete, consider a representative North East structural-steel fabricator supplying construction and infrastructure clients, running drilling lines, cold saws, shot-blast and heavy welding under EOT overhead cranes in a 2,600 square metre clear-span shed. This is an illustrative scenario, not a named client, but it reflects the pattern we see repeatedly. Two things drove the project: a doubled electricity bill on a tired incoming supply, and mounting pressure from main-contractor customers who had begun writing BES 6001 responsibly-sourced-steel and CBAM requirements into their pre-qualification questionnaires and supplier scorecards. The fabricator was losing marks at tender for having no on-site renewable line item, on work it had previously won on price alone.

The first task was the residual roof-load check. A structural engineer confirmed the frame could carry the array once the crane-rail dead loads were deducted, and the layout was designed to keep panels clear of the crane maintenance access. A 320 kW array of roughly 700 roof-mounted panels was sized to the half-hourly load, generating around 290,000 kWh a year at 83 percent self-consumption on the single-shift daytime pattern, for a payback near 4.2 years and roughly £61,000 of annual bill reduction. Just as valuable to this business, the renewable-energy share now reports directly into the customer's responsibly-sourced-steel and Scope 3 disclosures, and the on-site generation strengthened the fabricator's tender scores and protected its preferred-supplier position. The energy saving paid the finance; the tender advantage protected the order book. That dual return, hard cash plus procurement resilience, is why structural-steel customers increasingly treat solar as a commercial decision rather than an environmental one.

How we work

Our method for a structural-steel shop is deliberately load-led and evidence-led. We start with your half-hourly meter data, not a rule of thumb, and model the array to your real daytime consumption. In parallel we commission the structural survey, with the crane-rail and gantry residual-load check on heavy-lifting bays, and submit the G99 application so the grid clock starts on day one. We confirm the planning status, the roof condition and any asbestos, and design the layout around your LEV extraction penetrations and crane access. You receive a model you can interrogate, a fixed-price quote, and a clear comparison of buying outright against asset finance or a zero-capex Power Purchase Agreement, so the capital you would otherwise spend can stay with your fibre laser or press brake if you prefer. If the numbers do not stack up for your tenure or your roof, we will tell you plainly. When you are ready, the fastest first step is a free feasibility study: request one through our quote page. If your work spans more than steel, our sibling pages on laser and plasma cutting and welding and engineering workshops cover the load profiles of those trades in the same depth.