Current-Carrying Wiring Device Manufacturing (U.S.) — NAICS 335931

1. Overview

Every light switch you flip, every wall outlet you plug into, and the ground-fault outlets in your kitchen and bathroom are "current-carrying wiring devices." This industry makes the small, code-governed electrical parts that carry live current at the point where wiring meets a person or a machine: switches, receptacles (outlets), ground-fault and arc-fault protective devices, lamp holders, bus bars, and lightning/surge arrestors. The Economic Census questionnaire further specifies terminal blocks, pin-and-sleeve connectors, metal contacts, pressure and compression connectors, pre-insulated terminals, electric harnesses and assemblies, and special-purpose switches [1][2].

It is a high-volume, unglamorous components business. The products are cheap per unit but sold by the billions, they are largely non-discretionary (electrical code requires them), and demand tracks construction and renovation. The U.S. industry shipped about $8.4 billion of product in 2022 and employed roughly 24,400 people across about 397 plants [3][4].

Why an investor should care: this is a defensive, replacement-heavy manufacturing niche riding several structural tailwinds — data-center and factory construction, electrical-code changes that force more devices into each building, EV (electric-vehicle) charging, and reshoring. But it is cyclical with housing and highly exposed to the price of copper.

Ways in differ sharply between public and private investors. There is no U.S.-listed pure play — the two biggest American specialists, Leviton and Lutron, are private and family-owned [5][6]. Public-market investors get exposure only indirectly, through large diversified electrical companies for which wiring devices are one slice (Hubbell, Eaton, Legrand, Schneider Electric). Private investors can own the specialists, distributors, or smaller makers directly.

2. What it is and how it is structured

Scope. NAICS (North American Industry Classification System) code 335931 covers establishments primarily making current-carrying wiring devices: snap/tumbler/pushbutton/pressure switches, receptacles and outlets, GFCIs (ground-fault circuit interrupters), lamp holders, bus bars, non-switchgear electrical conductors, and lightning arrestors and coils [1].

What it excludes — this matters. The classification carves out several adjacent products that people casually lump together with "wiring":

• Electronic connectors (the pins-and-sockets that join circuit boards and cables) are NAICS 334417 — this is where Amphenol, TE Connectivity, and Molex mostly sit, so they are not primarily in 335931 despite showing up in some "wiring device" market reports [1][7].
• Non-current-carrying wiring devices — outlet boxes, faceplates/wall plates, conduit fittings, insulators, poles — are NAICS 335932 [1].
• Electronic-component sockets and switches are NAICS 334419 [1].
• Circuit breakers, panelboards, and switchgear are NAICS 335313, and wire and cable are NAICS 335921/335929 — a common point of confusion, since breakers and cable are sold alongside outlets.

Production process. Manufacturing combines metal stamping, casting, or machining; plating and contact fabrication; molding of thermoplastic or thermoset housings; purchase or fabrication of terminals, springs, screws, and electronic components; assembly; and electrical, endurance, and safety testing [2].

Ownership mix. The industry is not fragmented among mom-and-pops, nor is it a monopoly. Federal data count 359 firms operating 397 establishments in this code — so most companies run a single plant [3][4]. The economics are dominated at the top by a handful of large operators, but no one owns the category: the four largest firms make just 27.5% of shipments and the eight largest 38.8% [4]. Ownership falls into three buckets:

1. Divisions of big diversified electrical companies (public): Hubbell, Eaton (Arrow Hart brand), Legrand (Pass & Seymour), Schneider Electric (Square D), Siemens, ABB [8][9][10][11][12][13].
2. Large private specialists: Leviton (the biggest American pure-play, Melville, NY) and Lutron (the dimmer and lighting-control leader, Coopersburg, PA) [5][6][14][15].
3. Many small specialty shops making industrial, hospital-grade, marine, or niche devices.

3. How big it is

Federal statistics (our ground-truth figures):

That works out to about $343,000 of shipments per employee and an average wage near $69,000 [3][4]. The average plant employs roughly 60 people [3]. Concentration is low: the Herfindahl-Hirschman Index (HHI, a standard 0–10,000 concentration score) is just 313, well inside the range regulators consider unconcentrated, and even the top 50 firms make only 76.6% of shipments [4].

The undercount caveat — read this before quoting a bigger number. Federal figures measure domestic factory production. They do not count imports, and a large share of U.S. wiring-device consumption — especially commodity residential switches and outlets — is imported. So U.S. demand is meaningfully larger than the $8.4 billion of domestic output. Private market-research firms quote much bigger "U.S. wiring device market" numbers — roughly $11–17 billion for 2024 depending on the source, growing at mid-single digits [17][18] — but those figures use a broader product scope (often including distributor markup, faceplates, and sometimes electronic connectors) and count total consumption, not domestic manufacturing. Treat the $8.4 billion as the honest measure of what is made here, and the double-digit-billions figures as a broader consumption bundle. Also note the two federal years differ slightly (shipments are 2022; payroll/employment 2023).

Historical context. Factory-gate pricing has risen sharply: the BLS producer-price index for 335931 increased from 204.0 in June 2020 to 321.8 in June 2026, a calculated increase of 57.8% [19]. That measures selling prices, not real output or market growth; using nominal revenue without deflating would materially overstate unit-volume expansion.

4. The investable universe

There is no U.S.-listed company that only makes wiring devices. The two largest American specialists are private:

Private / not investable on public markets

Public — diversified companies with a wiring-device slice

Two cautions for stock pickers. First, for every name above, wiring devices are a minority of revenue — you are buying the whole company, not the outlet business. Hubbell is the closest large-cap proxy, but even there wiring devices sit inside a segment (Electrical Solutions) that is itself only about 36% of the company, the larger half being utility products [8]. Second, some "top wiring device manufacturer" lists include TE Connectivity or Molex — those are primarily electronic connector makers (NAICS 334417), a different industry [7].

5. How the money works

Owners in this industry make money the way volume component manufacturers do: cheap parts, enormous unit counts, and margin earned through product mix, scale, and cost pass-through.

• Unit economics and mix. A basic residential outlet or switch retails for roughly $1–$5; the raw device costs the maker cents. The money is in the mix: specification-grade commercial devices, hospital-grade, industrial high-amperage receptacles, GFCI/AFCI protection, tamper-resistant, USB, and "smart" connected devices all carry far higher prices and margins than the plain builder-grade outlet. Shifting the mix upward is the main lever on profitability.
• Input costs are the swing factor. The principal raw materials are copper (contacts and conductors), brass and zinc, steel, aluminum, and thermoplastics such as PVC (polyvinyl chloride) and nylon. Hubbell lists steel, aluminum, brass, copper, bronze, zinc, nickel, plastics, elastomers, petrochemicals, printed circuit boards, chips, and cord sets as principal inputs, with material costs approximately half of company cost of goods sold [21][23]. Copper is the dominant and most volatile cost. When copper spikes, gross margin compresses unless the maker can raise prices; the ability to pass metal costs through to distributors is a core competitive skill and a source of quarter-to-quarter margin cyclicality.
• Capacity utilization and operating leverage. Production runs on molds, stamping presses, and automated assembly with high fixed tooling cost. Once volumes cover the fixed base, incremental units drop heavily to profit — so capacity utilization through the construction cycle drives margins. Hubbell attributed approximately six percentage points of 2025 margin expansion to pricing, productivity, and volume, offset by approximately five points of contraction from material and other inflation, tariffs, and unfavorable mix [21].
• Channel and moat. Devices reach the market through electrical distributors (Rexel, Graybar, WESCO, Sonepar) for professionals and big-box retail (Home Depot, Lowe's) for residential. Hubbell notes its ten largest customers represent approximately 42% of company sales, demonstrating distributor and channel concentration [21]. The durable advantages are brand trust with electricians, shelf space and distributor relationships, breadth of catalog (thousands of SKUs, or stock-keeping units), and — critically — the safety certifications discussed below. A device that is not listed by a testing lab effectively cannot be sold or installed.
• Replacement demand cushions the cycle. With well over 140 million U.S. housing units plus a vast installed base of commercial and industrial buildings, a large share of demand is renovation, repair, and code-driven replacement rather than new construction — which softens downturns.

6. What drives demand

• Construction and renovation. New residential and non-residential building is the biggest single driver; remodeling and repair add a large, steadier base. Both move with interest rates, housing starts, and commercial construction cycles. Hubbell reported 2025 Electrical Solutions strength in data centers and light industrial markets offset by softness in nonresidential and heavy industrial markets, illustrating how end-market mix can matter as much as aggregate construction [21].
• Electrical-code content growth. Each revision of the National Electrical Code (NEC) tends to require more protective devices per building — expanding GFCI zones, AFCI (arc-fault circuit interrupter) coverage, and tamper-resistant receptacles [24]. More required devices per home is a structural, code-mandated tailwind independent of square footage. UL notes that special-purpose GFCI requirements will extend to specified refrigerated-transport receptacles effective January 1, 2029 [25].
• Data centers and AI buildout. Hyperscale and AI data-center construction is a major current driver of high-amperage industrial receptacles, busway/bus bars, and power-distribution devices; Hubbell specifically cited data-center and renewables strength behind its wiring-adjacent volume growth [8][26]. The Department of Energy reports that data centers' share of U.S. electricity consumption increased from 1.9% in 2018 to 4.4% in 2023 and could reach 6.7–12% by 2028 [27][28].
• Electrification and smart buildings. EV charging, USB-integrated outlets, connected switches and dimmers, and energy-management controls push the mix toward higher-value devices. Digitalization adds smart switches, sensors, controlled receptacles, and USB power delivery, increasing content per endpoint — but it also introduces semiconductor sourcing, software support, interoperability, cybersecurity, and obsolescence risks.
• Reshoring and industrial construction. New U.S. factories (semiconductors, batteries, and other reshored manufacturing) add industrial-grade device demand.

7. Regulation

Regulation shapes this industry less through licensing the makers and more through mandating what must be installed and how devices must be certified — both of which create and expand demand.

• National Electrical Code (NEC / NFPA 70). The NEC, published by the National Fire Protection Association and adopted (often with amendments) by states and municipalities, dictates where GFCI protection is required (Article 210.8), where AFCI protection is required (210.12), and where tamper-resistant receptacles are required (406.12) [24]. Code adoption cycles directly change how many and which devices go into every building.
• Safety listing by an NRTL. Devices must be tested and "listed" by a Nationally Recognized Testing Laboratory (most commonly UL) against product standards — for example UL 498 (receptacles and plugs), UL 20 (snap switches), UL 943 (GFCIs), and UL 1699 (AFCIs) [24][29][30]. Listing is effectively mandatory and is a real barrier to entry. Certification changes can require redesign, validation, and continuing factory surveillance.
• NEMA configurations. The National Electrical Manufacturers Association defines the standardized plug/receptacle configurations and dimensions that make devices interchangeable.
• Energy and building codes. State energy codes (California's Title 24 is the strictest) drive demand for lighting controls, occupancy sensors, and dimmers.
• Trade and tariffs. A large share of commodity devices is imported, so trade policy hits the industry directly. Section 301 tariffs on Chinese electrical goods (rates commonly 25–50%+ on strategic categories) and, from August 2025, a 50% tariff on copper-intensive derivative products raise both import prices and domestic input costs [31][32]. "Build America, Buy America" content rules on federally funded projects also favor domestic devices. Hubbell explicitly warns that tariffs can increase imported and domestically sourced material costs, disrupt supply chains, and reduce demand [21].

8. Competitive dynamics and consolidation

The competitive structure is a stable oligopoly-plus-fringe: several large diversified players, two strong private specialists, and a long tail of small makers, with no single firm dominant (top-four share just 27.5%) [4].

• Consolidation has been steady. The majors grew by acquisition — Eaton absorbed Cooper Industries (2012), bringing Arrow Hart into its portfolio; Legrand has been a serial acquirer of device and controls brands (Pass & Seymour, Wattstopper, and many more) [9][10]; Hubbell, Schneider, and ABB have all rolled up smaller makers.
• Barriers protect the premium end. Brand trust with electricians, mandatory safety listings, distributor shelf space, and catalog breadth defend the higher-margin specification, industrial, and hospital-grade business against low-cost imports. Imports compete hardest at the plain residential commodity end.
• Technology is blurring boundaries. Smart, connected devices bring software and electronics into what was a mechanical business, favoring scaled players who can invest — and inviting competition from electronics firms. Low-voltage and Power-over-Ethernet approaches could, over time, displace some traditional line-voltage devices.

9. Risks

• Housing and construction cyclicality. New-build demand swings with interest rates and construction cycles; a downturn hits volumes and plant utilization.
• Copper and commodity prices. Copper is the dominant input and is volatile; a spike squeezes margin until price increases catch up, and the 2025 copper tariff raises the input-cost floor [23][32].
• Tariff and import whipsaw. Trade policy cuts both ways — tariffs can protect domestic makers but also raise imported-component and raw-material costs; sudden changes disrupt sourcing.
• Channel concentration. Reliance on a few big distributors and big-box retailers gives buyers pricing leverage.
• Technology disruption. Smart-home and low-voltage architectures could erode the traditional device franchise for makers who don't invest.
• Regulatory double edge. Code changes drive demand but also force product redesign and re-certification cost; a missed listing or safety recall is expensive and reputationally damaging.
• Product safety and recall risk. A small manufacturing defect can create shock, overheating, or fire exposure. In 2020, CPSC announced a recall of approximately 98,000 Leviton connectors, plugs, receptacles, and inlets following mislabeled terminals [33]. The same year, Pass & Seymour recalled approximately 685,000 commercial-grade receptacles because a manufacturing error could cause overheating [34].
• Labor exposure. BLS reported a 2024 total-recordable injury and illness rate of 2.5 cases per 100 full-time workers for 335931, including 1.3 cases involving days away, restriction, or transfer [35].

10. How to invest and the outlook

Public-market routes. There is no clean pure play. The practical choices are diversified electrical companies where wiring devices contribute meaningfully but are not the whole story: Hubbell (HUBB) is the closest large-cap U.S. proxy, followed by Eaton (ETN) and the adjacent nVent (NVT); international exposure comes through Legrand (LGRDY), Schneider Electric (SBGSY), Siemens (SIEGY), and ABB (ABBNY) [8][9][10]. In every case you are buying a broad electrical franchise, and the outlet-and-switch business is a minority of it — so a device thesis has to be weighed against utility, industrial, and building-automation exposure. Public investors should model the relevant portfolio and end markets rather than apply an assumed 335931 market share to consolidated sales.

Private-market routes. The most direct exposure is unavailable to public investors and belongs to private owners: the specialists themselves (Leviton, Lutron) are family-held [5][6]. Private and search-fund investors instead target smaller specialty device makers (industrial, marine, hospital-grade), the electrical-distribution layer, and private-equity-backed building-products platforms rolling up niche electrical brands. Private-company diligence should reconstruct product-level revenue rather than rely on a corporate NAICS code. The critical questions are listing and certification ownership; share of commodity versus specification-grade products; distributor and customer rebates; exposure to copper and tariffs; domestic versus offshore tooling and production; SKU and inventory complexity; warranty and recall history; code-driven redesign requirements; plant utilization; and whether the establishment's primary activity genuinely belongs in 335931.

Outlook (forward-looking judgment). The reported backdrop is favorable and the structural drivers point up: electrical-code content growth, data-center and reshored-factory construction, EV charging, and smart-building upgrades should support mid-single-digit demand growth, and the large replacement base cushions downturns [17][18][26]. The clearest near-term swing factors are the housing/interest-rate cycle on the demand side and copper prices plus tariff policy on the cost side. A reasonable expectation is a steady, defensive, modestly growing manufacturing niche — attractive for its non-discretionary, code-driven demand, but one where margins in any given year are set as much by copper and construction as by the underlying secular trends. These are judgments about direction, not guarantees.

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Sources

1. U.S. Census Bureau. "2022 NAICS Definition — 335931 Current-Carrying Wiring Device Manufacturing." 2022. https://www.census.gov/naics/?input=335931&year=2022
2. U.S. Census Bureau. "2022 Economic Census Questionnaire, MC-33594." 2022. https://bhs.econ.census.gov/ombpdfs2022/export/2022_MC-33594_su.pdf
3. U.S. Census Bureau. "County Business Patterns (CBP), NAICS 335931." 2023. https://www.census.gov/programs-surveys/cbp.html
4. U.S. Census Bureau. "2022 Economic Census — Concentration Ratios / Shipments, NAICS 335931." 2022. https://www.census.gov/programs-surveys/economic-census.html
5. Wikipedia / PitchBook. "Leviton Manufacturing Company." 2026. https://en.wikipedia.org/wiki/Leviton
6. Architect Magazine. "Lutron to Remain Private, Family-Owned Business." https://www.architectmagazine.com/technology/lighting/lutron-to-remain-private-family-owned-business_o
7. Market Data Forecast. "North America Connector Market Size, Share & Trends." 2025. https://www.marketdataforecast.com/market-reports/north-america-connector-market
8. Hubbell Incorporated. "Fourth Quarter 2024 and Full Year Results." 2025. https://hubbell.gcs-web.com/news-releases/news-release-details/hubbell-reports-fourth-quarter-2024-and-full-year-results
9. Eaton. "Arrow Hart Wiring Devices." https://www.eaton.com/us/en-us/products/wiring-devices-connectivity/arrow-hart.html
10. Legrand. "2024 Full-Year Results." 2025. https://www.legrand.com/en/news/2024-full-year-results
11. NEMA. "Hubbell Incorporated Member Profile." https://www.nema.org/membership/manufacturers/view/hubbell-incorporated
12. NEMA. "Eaton Member Profile." https://www.nema.org/membership/manufacturers/view/Eaton
13. NEMA. "Legrand North America Member Profile." https://www.nema.org/membership/manufacturers/view/legrand-north-america
14. NEMA. "Leviton Manufacturing Member Profile." https://www.nema.org/membership/manufacturers/view/leviton-manufacturing-co-inc-
15. NEMA. "Lutron Electronics Member Profile." https://www.nema.org/membership/manufacturers/view/lutron-electronics-company-inc-
16. U.S. Small Business Administration. "Table of Size Standards, NAICS 335931 (600 employees)." 2023. https://www.sba.gov/document/support-table-size-standards
17. Renub Research. "United States Wiring Devices Market Growth Forecast 2025–2033." 2025. https://www.renub.com/united-states-wiring-devices-market-p.php
18. IBISWorld. "Wiring Device Manufacturing in the US — Market Size." 2026. https://www.ibisworld.com/united-states/industry/wiring-device-manufacturing/807/
19. Bureau of Labor Statistics / FRED. "Producer Price Index: Current-Carrying Wiring Device Manufacturing (PCU335931335931)." https://fred.stlouisfed.org/series/PCU335931335931
20. Leviton. "About Leviton." https://leviton.com/company/about-leviton1
21. U.S. Securities and Exchange Commission. "Hubbell Inc. Form 10-K, FY2025." 2026. https://www.sec.gov/Archives/edgar/data/48898/000162828026007500/hubb-20251231.htm
22. Legrand. "Key Figures 2025." https://www.legrand.com/en/group/legrands-key-figures/2025
23. IMARC Group / Encore Wire Corp Form 10-K (raw-material cost composition, copper/PVC). 2023. https://www.imarcgroup.com/insight/understanding-the-economics-a-copper-wire-manufacturing-case-study
24. EC&M / Eaton. "NEC Requirements for GFCIs and AFCIs; UL 943 / UL 1699 Listing." https://www.ecmweb.com/national-electrical-code/code-basics/article/21280067/nec-requirements-for-gfcis-and-afcis
25. UL. "Special-Purpose Ground-Fault Circuit Interrupters Guidance." https://www.ul.com/thecodeauthority/knowledge/special-purpose-ground-fault-circuit-interrupters
26. Mordor Intelligence. "Data Center Wire and Cable Market Trends & Share." 2025. https://www.mordorintelligence.com/industry-reports/data-center-wire-and-cable-market
27. U.S. Department of Energy. "Geothermal and Data Centers." https://www.energy.gov/hgeo/geothermal/geothermal-and-data-centers
28. Lawrence Berkeley National Laboratory. "2024 LBNL Data Center Energy Usage Report." https://energyanalysis.lbl.gov/publications/2024-lbnl-data-center-energy-usage-report
29. UL. "UL White Book — Electrical Equipment Guide." https://code-authorities.ul.com/wp-content/uploads/2014/09/UL-White-Book.pdf
30. UL. "GFCI Personal Protection Devices Testing and Certification." https://www.ul.com/services/gfci-personal-protection-devices-testing-and-certification
31. White & Case LLP. "United States Finalizes Section 301 Tariff Increases on Imports from China." 2024. https://www.whitecase.com/insight-alert/united-states-finalizes-section-301-tariff-increases-imports-china
32. China Briefing. "US-China Tariff Rates (incl. 50% copper-derivative tariff, Aug 2025)." 2025. https://www.china-briefing.com/news/us-china-tariff-rates-2025/
33. U.S. Consumer Product Safety Commission. "Leviton Manufacturing Recalls Electrical Connection Devices Due to Shock Hazard." 2020. https://www.cpsc.gov/Recalls/2020/Leviton-Manufacturing-Recalls-Electrical-Connection-Devices-Due-to-Shock-Hazard
34. U.S. Consumer Product Safety Commission. "Pass & Seymour/Legrand Recalls Electric Outlets Due to Fire Hazard." 2020. https://www.cpsc.gov/Recall-Products/Electric-Outlets-or-Receptacles
35. Bureau of Labor Statistics. "2024 Industry Injury and Illness Incidence Rates." https://www.bls.gov/web/osh/table-1-industry-rates-national.htm