Welding & Engineering Workshops: Solar panels for fabrication

Why welding and engineering workshops are one of the strongest solar fits in the country

Sub-contract welders and jobbing engineering shops run exactly the load pattern that makes solar pay. The work is single-shift, Monday to Friday, in daylight hours, so electrical demand lands almost perfectly on top of the solar generation curve. That match is the whole game: when your demand and your generation happen at the same time of day, 70 to 90 percent of everything the array makes is consumed on site at your full import rate of around 25 to 30p per kWh, rather than being spilled onto the grid for a fraction of that under an export tariff. High self-consumption is what drives short paybacks, and a welding shop has it built in, unlike a house that sits empty all day or a 24/7 process plant that exports far more of its midday output.

The load profile itself is the detail generalist installers miss. A welding and engineering workshop runs a spiky, high-power set of processes, MIG, MAG, TIG and MMA welding sets, plasma cutters, grinders, drills and saws, that switch on and off through the day. On their own those spikes look like a difficult match for solar. But they do not sit on their own: they sit on top of a large, near-constant daytime baseload. A rotary-screw compressor cycles all day to hold line pressure for tools, clamps and plasma. The legally-required LEV weld-fume extraction runs whenever anyone strikes an arc. Between them, the compressor and the extraction form a steady anchor load that solar feeds smoothly, while the welding, grinding and cutting peaks soak up midday generation on top. The result is that even a smaller jobbing unit reaches the near-total daytime self-consumption that shorter paybacks depend on.

The commercial logic is just as clean. Industrial electricity roughly doubled between 2021 and 2024, and for a shop that wins work on fixed-price competitive tenders, power is now the biggest controllable cost after steel and labour, and a cost you cannot always pass on. A rooftop array hedges a large slice of that bill at a fixed lifetime cost for 25 years. On top of the savings, it puts an on-site renewable line item on the table that automotive, rail, construction-steel and offshore customers increasingly ask for in their supplier questionnaires, so the roof earns its keep at tender as well as on the meter. You can put your own numbers through our savings calculator to see the shape of it before you speak to anyone.

The typical install for a welding and engineering workshop

A welding and engineering workshop solar system in the UK typically runs from 40 to 200 kW, using roughly 90 to 440 panels and 240 to 1,200 square metres of roof. That span covers the sector well: a small sub-contract welding or jobbing unit sits near the lower end at 40 to 75 kW, while a larger multi-bay engineering shop with several welding stations, saws and machining runs up toward 200 kW. Project values run from around £30,000 for a compact welding unit to about £150,000 for a larger engineering workshop, and paybacks average around five and a half years, a little longer than a big laser-profiling or structural-steel plant only because the units are smaller, and still well inside the roof's 25-year working life.

We do not size to roof area, we size to your daytime load, and welding shops make that straightforward because the load is naturally daytime-weighted. The method is to pull 12 months of half-hourly meter data from your supplier and model the array so annual generation matches roughly 70 to 90 percent of daytime consumption. As a working guide, 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 700 square metre workshop roof will usually carry somewhere around 90 to 130 kWp depending on obstructions. We anchor the design on the loads that run all day, the compressor first, then the LEV extraction, then any continuous ancillaries, and let the spiky welding and cutting peaks feed off the midday surplus. Portal-frame single-pitch roofs on trading-estate units are usually clean, accessible and well suited to rail-fixed PV, which keeps the installation efficient and the cost per kWp competitive. For a fuller breakdown of what drives system cost at each size, see our cost guide.

A costed, illustrative scenario

The figures below are illustrative and representative, not a named client, but they reflect the economics we see on a typical mid-size welding and engineering workshop. Take a shop running four to five welding stations, a bank of grinders and saws, whole-shop LEV extraction and a 30 kW rotary-screw compressor on a single day shift, in a 700 square metre portal-frame unit.

Item	Illustrative figure
System size	90 kW (around 200 panels, roof-mounted)
Indicative project value	£68,000
Annual generation	82,000 kWh
Self-consumption	Around 88 percent on a single-shift daytime load
Annual bill reduction	£17,500 in year one, escalating with grid tariffs
Simple payback	Around 5.4 years

Roughly 88 percent of what the array generates is used on site at the full import rate, because the compressor and extraction hold a steady daytime floor that solar feeds directly, and the welding peaks land squarely in the middle of the day when generation is highest. The small surplus that does spill is paid for under the Smart Export Guarantee at a supplier-set rate, typically around 12 to 16p per kWh in 2026, quoted as a range because suppliers set it rather than Ofgem. For a profitable limited company buying outright, the Annual Investment Allowance gives 100 percent year-one tax relief on the first £1m of qualifying spend, which covers a system of this size in full and is worth up to roughly a quarter of the cost against corporation tax. Solar is special-rate plant, so it does not qualify for full expensing or the new 40 percent first-year allowance, a distinction we set out in full on the grants and funding page. On-site solar and any co-located battery are also exempt from business rates in England to 31 March 2035. All tax and payback figures here are illustrative and depend on your profits and tax position, so confirm them with your accountant or HMRC before you commit.

The compliance that is specific to a welding shop

Welding compliance is where a specialist earns its place, because the single biggest constraint on the roof of a welding shop is not structural, it is fume extraction. Under the HSE welding-fume duty (Safety Bulletin STSU1-2019), all welding fume, including mild-steel fume, is now classed as a Group 1 carcinogen. General ventilation is no longer considered adequate: Local Exhaust Ventilation is required for all indoor welding regardless of duration or material, supplemented by respiratory protective equipment where LEV alone does not control exposure, under COSHH 2002. That LEV plant is not optional and it does not switch off. It also penetrates and discharges through the same roof that carries the array, so weld-fume discharge stacks, air-handling and the PV layout have to be designed together, not in sequence. We plan panel positions, cable routes and maintenance walkways around your existing and planned extraction penetrations so the PV never blocks a legally-required fume route, and we keep the extraction running through the works. The background to the duty is set out in the HSE guidance on welding-fume health risks. As a practical benefit, that mandatory extraction is itself an obligatory daytime load the solar offsets pound for pound, whenever anyone welds, the array is already carrying part of the extraction bill.

The electrical side has its own trade-specific detail. Any inverter output above 16 A per phase, about 3.68 kW single-phase or 11 kW three-phase, needs a G99 application to the local Distribution Network Operator before connection, so a commercial welding array is essentially always G99. For a welding shop the G99 sizing has to account for welder inrush and power-factor, because arc-welding sets draw heavy transient current and can pull the power factor around, so the connection study looks at more than a simple nameplate total. We submit that application on day one, alongside the survey work, so the connection clock starts immediately rather than at contract, which is often the longest single item in the programme. Where a heavier engineering shop also runs plasma cutting, those cutters usually need dedicated circuits and can trigger a supply or breaker upgrade that a survey should surface early. Most industrial rooftop PV is Permitted Development under Class A of Part 14 of the GPDO 2015, and the previous 1 MW cap was removed in December 2023, so even a large array on a welding unit rarely needs a planning application, subject to the projection limits of 200mm above a sloping roof or 600mm above a flat roof, and the usual exclusions for listed buildings, conservation areas and Article 4 directions. Any pre-2000 unit needs an asbestos management survey first, because asbestos-cement roofs cannot take rooftop PV directly, and a structural engineer checks the portal frame before install, since a framed array adds roughly 15 to 25 kg per square metre plus wind uplift. Rooftop-PV fire safety follows the RC62 Code of Practice, which insurers increasingly make a condition of cover, so we notify your property insurer and obtain sign-off before work starts.

An illustrative case scenario

The following is an illustrative, representative scenario rather than a named client, but it reflects a common welding-shop situation, particularly the tenure question that comes up on leased units. Picture a sub-contract welding and jobbing engineering firm on a five-year lease in a 700 square metre unit, running spiky MIG and TIG loads on top of a compressor and whole-shop LEV extraction. Margins on their tendered work were tight and the remaining lease term ruled out a large capital spend, so a route that needed no up-front cash was the priority.

The design placed a 90 kW array, around 200 panels, around the existing weld-fume extraction stacks so the LEV runs untouched. Because the shop works a single day shift, self-consumption modelled at close to total, with almost every generated kWh feeding the compressor, extraction and welding load directly. Rather than a capital purchase the system was funded through a Power Purchase Agreement with landlord consent: a funder owns the array, and the fabricator simply buys the solar power at a fixed rate below grid for the life of the lease, paying nothing up front. The outcome was a lower, more predictable electricity cost from day one, an on-site renewable line item to put in front of tendering customers, and no drain on the capital budget the owner wanted to keep free for plant. Where a shop owns its unit outright the same result comes more simply through a cash purchase or asset finance spread over five to seven years, usually cash-flow positive from month one because the finance payment is smaller than the bill it replaces.

How we work

Every welding and engineering shop is different, so we start from your actual data, not a rule of thumb. We pull and model your half-hourly meter data, size the array to your real welding, extraction and compressor load, survey the roof for structure and asbestos, and design the PV around your fume-extraction penetrations before a single panel is ordered. We submit the G99 application on day one, handle the RC62-compliant fire-safe design and insurer sign-off, and model cash, asset finance and PPA side by side so you can compare like for like on your own terms. If the tenure or the roof does not stack up, we will tell you honestly. If you run a larger machining operation alongside the welding, our CNC machining shops page covers that load profile in the same detail. When you are ready, the fastest way to a real number for your unit is to request a fixed-price quote, and we will turn a free feasibility study around quickly.