Almost everything Britain wants to build over the next decade is, at bottom, electrical — data centres, grid connections, battery storage, EV charging, heat pumps — and the accounts of the 281 UK electrical-installation companies that publish a full profit-and-loss show the boom arriving: £13.3bn of combined turnover, roughly nine in ten companies profitable, and a growth table that reads like an itinerary of the energy transition. What the boom hasn’t changed is who gets paid for it. TClarke, the country’s biggest specialist electrical contractor and a data-centre house, turned £846.7M of work into £16.3M of profit — a 1.9% margin, over a 15-month period to March 2025 after a year-end change (the prior 12 months came to £491.0M). One rung down, the firms that own a niche keep five to ten times that: Powersystems, an employee-owned high-voltage contractor, makes 12% connecting wind farms and battery storage to the grid, and Aidan Strain Electrical Engineering, a Newry family firm wiring data centres across Europe, grew turnover 126% and still kept a 15.7% margin. Figures are approximate — verify against a company’s own accounts before relying on any single number.
Read the wires first
Four things change how you read every number below.
Not everything on this shelf is an electrical contractor. The category’s giants include some neighbours in the same registration band doing quite different work: Altrad Services (£550.9M) is an industrial-services business — scaffolding, insulation, coatings for oil, gas and power sites; Nordex UK (£225.7M) is a German wind-turbine maker’s British build-and-service arm; and British Gas New Heating (£344.8M) is Centrica’s domestic heating-installation business, a consumer trade with consumer economics. They’re labelled in the giants table and kept out of every competitive read.
The groups file in layers. Dalkia Engineering (£234.3M) sits inside Dalkia Group, and Gratte Brothers Limited (£199.6M) inside Gratte Brothers Group — the giants table uses one group-level entity per group.
What you see is the top of the trade. Tens of thousands of electrical firms — the one-van electricians and small local contractors — file accounts too small to carry a profit figure and don’t appear here at all. This map covers the commercial and industrial top slice, which is exactly where the data-centre and grid money lands.
Margin is not margin across models. A lump-sum installation contractor passes enormous material and subcontract costs through its top line and keeps a sliver; a maintenance business earns repeat framework revenue on its own labour; an in-house arm of a larger group prices work for its parent. Comparing their percentages tells you about their models, not their management — so this report doesn’t.
The giants: national scale, contractor’s sliver
| Company | What it is | Turnover | PBT | TO YoY | Staff YoY |
|---|---|---|---|---|---|
| TClarke | specialist electrical/M&E, data-centre heavy | £846.7M (15 mo)* | £16.3M | — | — |
| Dalkia Group | EDF’s UK technical & energy services group | £656.6M | £8.2M | +8% | +29% |
| Altrad Services | industrial services (access, insulation) | £550.9M | £37.3M | +13% | — |
| NG Bailey | family-owned independent M&E group | £346.1M | £6.2M | +11% | +2% |
| British Gas New Heating | Centrica’s domestic heating-install arm | £344.8M | −£16.6M | −13% | +20% |
| EMCOR Group (UK) | facilities & engineering services; now OCS FM (acquired by OCS Group, Dec 2025) | £333.0M | £21.1M | −5% | −7% |
| Phoenix ME | London M&E, data-centre fit-out | £319.1M | £16.6M | +8% | — |
| C.L.C. Contractors | property maintenance & refurbishment, HIG Capital-owned | £287.6M (15 mo)* | £38.4M | — | — |
| Gratte Brothers Group | family M&E group (buildings, catering, security) | £242.5M | £4.4M | −8% | +0% |
| Nordex UK | wind-turbine maker’s build & service arm | £225.7M | £3.3M | +105% | +6% |
Group entities: Dalkia Engineering (£234.3M, £9.0M) sits inside Dalkia Group’s figures; Gratte Brothers Limited (£199.6M, £3.6M) inside Gratte Brothers Group’s. *TClarke’s and C.L.C.’s latest accounts cover 15-month periods to March 2025 after year-end changes — annual scale is roughly a quarter lower (TClarke’s prior 12 months: £491.0M), though the margins are unaffected. EMCOR Group (UK)‘s figures are its final year under US owner EMCOR; OCS Group completed its acquisition in December 2025 and the company now trades as OCS FM.
Line up the genuine contractors and the margins cluster tight: TClarke at 1.9%, NG Bailey at 1.8%, Gratte Brothers at 1.8%, Dalkia at 1.2%. These are the same economics we mapped in building contractors — someone else’s project, a contracted price, all the delivery risk, and a sliver kept at the end — and no amount of data-centre demand has repriced them. The exceptions in the table prove the models rule: EMCOR’s 6.3% blends facilities-management contracts with engineering; C.L.C.’s 13.4% is a maintenance-and-refurbishment book — painting, compliance and repair frameworks for social housing — which is repeat revenue on its own labour, not lump-sum contracting; and Altrad’s 6.8% is industrial services, a different trade altogether.
Two rows carry the drama. Phoenix ME grew 74% in its year to September 2024, to £295.3M — a data-centre-driven ramp, with headcount up a more sober 13% — and kept only 3.6% of it; that is what a boom looks like inside contracting economics, where one late, mispriced or disputed job can wipe the year. Its newest accounts, to September 2025, show the ramp holding (£319.1M, +8%) and the margin recovering to 5.2%. And British Gas New Heating posted the giants’ one big loss: −£16.6M on revenue down 13%, while hiring 20% more staff as Centrica pivots the business toward heat pumps and EV charging — the boiler-install core remained loss-making.
The shape of the trade
Above £1M of turnover, this is one of the healthiest trades we’ve mapped: roughly nine in ten companies in every band are profitable, all the way up to the giants. The thin £1–5M band isn’t a graveyard — it’s a reporting artefact. Full profit-and-loss publication effectively starts at audit scale, so the map jumps almost straight from the invisible small trade to the £5M-plus commercial tier.
Where the margins are: own a niche, not a scale
The mid-market screen — profitable operators at £5–100M clearing at least a 5% margin, a bar the national giants don’t reach — is where this trade’s money actually sits.
| Company | What it does | Turnover | PBT | Margin | Trajectory |
|---|---|---|---|---|---|
| Irwin M&E | NI mechanical & electrical | £76.1M | £6.6M | 8.7% | growing |
| MAP Group (UK) | electrical & telecoms networks | £74.4M | £10.9M | 14.7% | stable |
| Wingate Electrical | London electrical contractor | £71.9M | £8.3M | 11.6% | stable |
| Bancroft | electrical contractor | £69.6M | £3.9M | 5.6% | stable |
| Powersystems UK | high-voltage grid connections | £63.5M | £7.6M | 12.0% | growing |
| UK Power Networks Services (Commercial) | utility group’s commercial arm | £61.0M | £7.4M | 12.1% | stable |
| Smith and Byford | housing maintenance & compliance | £58.5M | £6.5M | 11.1% | stable |
| Cema Group | electrical & engineering group | £57.9M | £5.6M | 9.7% | stable |
| Michael Nugent | NI electrical contractor | £57.1M | £3.2M | 5.6% | growing |
| Munro Building Services | London M&E | £56.1M | £3.0M | 5.4% | growing |
| Gloster MEP | M&E fit-out | £54.2M | £3.9M | 7.2% | stable |
| Halsall Mechanical & Electrical | Merseyside M&E | £53.2M | £9.4M† | 17.6%† | shrinking |
| Actemium UK | Vinci’s industrial-process brand | £52.0M | £4.5M | 8.7% | growing |
| Premier Electrics | NI electrical, UK & Ireland fit-out | £51.7M | £9.7M | 18.7% | stable |
And six more clear the same bar, from East West Connect to John G. Mackintosh. One company the screen surfaced is excluded above: Journeo, an AIM-listed transport-technology firm (displays and CCTV for buses and rail) that shares the registration band but isn’t an electrical contractor. Note also that UK Power Networks Services (Commercial) is an arm of London’s electricity-network group rather than an independent, and Actemium is Vinci-owned. †Halsall’s £9.4M PBT is a one-off: its own accounts attribute it to a related-company loan write-off, without which profit before tax would have been £96k — an underlying trading margin near 0.2% — and turnover fell 24% year-on-year.
The pattern is consistent: the premium is in the niche, not the size. Powersystems (12.0%, employee-owned) is one of a handful of accredited independent connection providers plugging wind, solar and battery projects into the grid at up to 132kV — scarce accreditation, scarce skills, priced accordingly. Premier Electrics (18.7%) runs repeat fit-out and framework work at margins a national M&E house would not recognise — and has now held them across two consecutive years. Smith and Byford (11.1%) earns maintenance-book economics, like C.L.C. above. And there’s a distinct Irish Sea cluster — Irwin M&E, Michael Nugent, Premier Electrics, Aidan Strain — Northern Irish contractors exporting into European and British commercial work, several of them at the top of both the margin and growth tables.
Growth, read with care — an itinerary of the energy transition
Sorted by growth, this table is a map of where Britain’s electrification money is landing. Heat pumps: Aira Home UK, the Swedish-backed installer, +361% with headcount +204%. Data centres: King & Moffatt UK, the British arm of an Irish M&E group, +153%; Aidan Strain +126%; Phoenix ME +74%. Grid and solar: Ethical Power Connections +107%; Powersystems +76%. Wind: Nordex UK +105% (the turbine maker’s arm — a demand signal, not a competitor).
| Company | Turnover | PBT | Margin | TO YoY | Staff YoY |
|---|---|---|---|---|---|
| Aira Home UK | £30.1M | £1.1M | 3.6% | +361% | +204% |
| King & Moffatt UK | £94.5M | £1.5M | 1.6% | +153% | +24% |
| Michael Nugent (ES) | £25.6M | £211k | 0.8% | +132% | +15% |
| Aidan Strain Electrical Engineering | £102.6M | £16.1M | 15.7% | +126% | +50% |
| Ethical Power Connections | £81.9M | £959k | 1.2% | +107% | +58% |
| Nordex UK | £225.7M | £3.3M | 1.5% | +105% | +6% |
| Murphy Technical Services | £25.8M | £5.0M | 19.5% | +88% | — |
| Michael Nugent | £57.1M | £3.2M | 5.6% | +86% | +24% |
| Powersystems UK | £63.5M | £7.6M | 12.0% | +76% | +22% |
| Phoenix ME (yr to Sep 2024) | £295.3M | £10.7M | 3.6% | +74% | +13% |
Unusually for a growth table, most of this is believable: nearly every fast grower is hiring hard behind the revenue — Aira +204% staff, Ethical Power +58%, Aidan Strain +50% — which is real capacity being built for real workload, not acquisition accounting. One number to discount: Aira’s small profit is flattered by a one-off fair-value credit — underlying trading is still loss-making, funded by its Swedish parent. What’s thinner is the price of the ramp. King & Moffatt more than doubled to £94.5M and kept 1.6%; Ethical Power doubled to £81.9M and kept 1.2% — growth bought close to cost, presumably to establish position in a booming queue of grid and data-centre work. The standout is Aidan Strain: +126% to £102.6M and a 15.7% margin, the rare firm being paid a specialist’s price for a boom-time ramp — a rebound year after the ISG collapse hit it in 2024, and almost all of it earned in Europe (UK turnover was just £7.4M of the £102.6M). One line to read differently: Murphy Technical Services’ 19.5% is the in-house electrical arm of the Murphy construction group — work priced within a group, not a market margin.
Market structure: a fragmented trade, and that’s the point
The top five companies hold just 20.6% of the £13.3bn mapped here — half road freight’s concentration — and the curve flattens quickly: the top 50 hold 62.9%. Electrical contracting stays fragmented because scale buys no margin (the biggest firm in the trade keeps 1.9%); there is no cost curve to consolidate down, only regional reputations and framework relationships that don’t transfer in a deal.
Ownership and vintage: family wiring, private-equity interest
This is a founder-and-family trade — 156 of the 281 companies are individual-owned against 120 corporate-owned, and the name over the door is often still the founder’s (Strain, Nugent, Gratte, Mercer, Mackintosh). The oldest cohort is the biggest: 82 companies pre-date 1990, and only 8 were incorporated since 2021 — in contracting, clients pick the firm that has visibly survived cycles, so age functions as a moat and nobody storms in from scratch. But about 17% (49 companies) carry a Holdings/Group/Topco-style name, often the structural fingerprint of a buyout or a planned exit — though some are simply family group structures, NG Bailey and Gratte Brothers among them — noticeably more than in general building. And the giants table already holds one confirmed buyout: C.L.C. has been owned by private-equity firm HIG Capital since 2023 — a sign investors have already spotted what this report maps: double-digit-margin niches inside an essential, booming trade.
What the map shows
- The electrification boom is real and staff-backed. The fastest growers are hiring as hard as they’re billing — heat pumps (Aira +361%), data centres (King & Moffatt +153%, Aidan Strain +126%), grid connections (Ethical Power +107%, Powersystems +76%).
- Scale still earns a contractor’s sliver. TClarke, NG Bailey, Gratte and Dalkia cluster at 1–2% — the same economics as building contractors, un-repriced by the boom.
- The niches earn the money: high-voltage grid connections (Powersystems, 12%), data-centre wiring (Aidan Strain, 15.7%), maintenance books (C.L.C. 13.4%, Smith and Byford 11.1%), and repeat fit-out (Premier Electrics 18.7%, held across two consecutive years).
- Most boom-time growth is being sold near cost — King & Moffatt and Ethical Power doubled at 1–2% margins; Aidan Strain is the rare firm paid a specialist’s price for the ramp.
- A Northern Irish cluster punches far above its weight, exporting data-centre and commercial electrical skills into Europe and Britain from the top of both the margin and growth tables.
- It’s a family trade that private equity has noticed — 156 of 281 companies are individual-owned, but 17% carry buyout-style holding names (some of them family groups), and C.L.C. is already a HIG Capital portfolio company.
Methodology and caveats
This covers the 281 UK electrical-installation companies that publish a full profit-and-loss, out of a register of around 2,600 — the tens of thousands of small electrical firms below reporting scale are invisible here, so the map shows the commercial and industrial top of the trade. Businesses that share the registration band but do different work (industrial services, turbine manufacture, domestic heating, transport technology) are labelled and excluded from competitive reads; business-type labels are directional. Group holding companies and trading arms can both publish accounts, so the largest groups are shown once with subsidiaries noted. Margins are not comparable across installation, maintenance and in-house models, and one bad contract can swing a contractor’s year either way. Figures are approximate — verify against a company’s own accounts before relying on any single number. This is analysis, not financial advice.