Commercial Electrical Work UK — Moving from Domestic to Commercial and Industrial (2026)

Domestic vs commercial electrical work: the key differences

Moving from domestic to commercial work is not simply a change of venue. The scale, technical complexity, client relationships, and commercial structure are all fundamentally different. Understanding these differences before you make the transition will save you from pricing mistakes, compliance gaps, and awkward conversations on site.

• Scale and complexity: commercial projects involve larger distribution boards, sub-mains, multiple consumer units or MCCBs, and often three-phase supplies rather than single-phase domestic feeds.
• Voltage systems: three-phase 415V (line-to-line) or 230V (line-to-neutral) is standard in commercial premises. Industrial sites may also have motor control circuits, variable speed drives, and specialist equipment supplies.
• Certification regime: Part P is domestic-only. Commercial work falls under the Electricity at Work Regulations 1989 and broader health and safety legislation. You still issue Electrical Installation Certificates (EICs) but the building control notification route changes entirely.
• Client type: instead of a homeowner making emotional decisions, you deal with procurement managers, facilities managers, main contractors, or property developers who make decisions on cost, programme, and compliance evidence.
• Payment terms: domestic work is typically paid on completion or by stage. Commercial work usually runs on 30-day payment terms, often with 5% retention held back until practical completion and defects sign-off.
• Procurement process: commercial clients issue tenders, request PQQs (pre-qualification questionnaires), and often require you to be on an approved supplier list before they will consider your company.

None of this should put you off. The margins available in commercial work are often significantly better than domestic once you understand how to price and manage jobs correctly.

BS 7671 18th Edition Amendment 2 (2022): what changed for commercial work

BS 7671 (the IET Wiring Regulations) is the core standard governing all electrical installation work in the UK. The 18th Edition Amendment 2, which came into force in March 2022, introduced several changes that are particularly relevant to commercial and industrial projects.

• AFDD requirements (Regulation 421.1.7): Arc Fault Detection Devices are now required for certain circuits in higher-risk premises including student accommodation, care homes, and some commercial properties. You need to understand which premises types trigger the requirement and how to specify and install AFDDs correctly.
• EV charging provisions: Amendment 2 significantly expanded Section 722 covering electric vehicle charging installations. New requirements cover load management, protective devices, and earthing arrangements — directly relevant if you intend to offer commercial EV charge point installation as part of your commercial offer.
• Special installations: Part 7 of BS 7671 covers locations with special requirements. For commercial work this includes medical locations (Section 710), swimming pools and other basins (Section 702), and potentially explosive atmospheres (Section 706). Each section introduces additional or modified requirements on top of the general rules.
• Surge protection: Regulation 443.4 clarified when SPDs (surge protection devices) are required. In commercial settings — particularly where data, communications, or sensitive equipment is present — this is increasingly a baseline expectation rather than an optional extra.

Staying current with BS 7671 is not optional. Clients, insurers, and other contractors will assume you are working to the latest edition. NICEIC and NAPIT update their approved contractor assessment criteria accordingly.

Certification for commercial work: what Part P does and doesn't cover

Part P of the Building Regulations applies only to domestic electrical work in England. It does not apply to commercial premises. This is a common point of confusion for electricians making the transition, and it matters practically.

• Electricity at Work Regulations 1989: this is the primary legislation covering commercial and industrial electrical installations. It places a duty on employers (and the self-employed) to ensure electrical systems are safe and maintained. Non-compliance carries criminal liability, not just a civil claim.
• Health and Safety at Work Act 1974: the overarching framework. As a contractor working on commercial premises, you owe a duty to your own workers and to others who might be affected by your work.
• Premises-specific regulations: some commercial premises have additional requirements layered on top. HMOs (Houses in Multiple Occupation) are regulated by the Housing Act 2004 and local licensing conditions. Healthcare premises must comply with HTM 06-01. Petroleum storage sites and fuel filling stations have their own inspection and certification requirements.
• Building Regulations notification: commercial building work may require Building Regulations approval via the local authority or an approved inspector, but this is a building control matter, not a competent person scheme notification as it is in domestic work. Your role is to install to BS 7671 and certify accordingly — the developer or main contractor handles the planning and building control interface.

Types of commercial electrical work

Commercial electrical work covers a wide range of project types. Understanding which areas you can credibly offer — and where you need additional training or sub-contractors — is essential before you start quoting.

• Office fit-outs: new or refurbished office space typically needs first and second fix wiring, containment, distribution boards, lighting circuits, small power, data cabling infrastructure, and emergency lighting. A well-rounded electrical package in a medium office can run to £50,000–£150,000+ depending on size and specification.
• Retail lighting: track lighting, LED panels, display lighting, feature lighting, and external signage supplies. Retail clients are increasingly specification-driven and often work with lighting designers whose specs you will be expected to deliver.
• Industrial three-phase installations: motor supplies, compressors, CNC machinery, welding equipment, industrial ventilation, and three-phase distribution boards. This is where knowledge of motor control, contactor panels, and industrial distribution becomes essential.
• Data and communications infrastructure: Cat6 and fibre backbone cabling is often included in an electrical package on smaller commercial fit-outs. Know where your competence ends — structured cabling for large data centres or server rooms is specialist work. Many electricians draw the line at Cat6 patching and leave active rack equipment and testing to IT specialists.
• Emergency lighting (BS 5266): virtually all commercial premises require emergency lighting. Design, supply, installation, and commissioning to BS 5266-1 is a distinct package that can be priced and sold separately or bundled into the wider electrical package.
• Fire alarm systems (BS 5839): commercial fire alarm design and installation requires specific third-party certification — typically BAFE SP203 or equivalent. Without this, you should not be designing and commissioning fire alarm systems. You can install cable and devices as part of a larger team, but the overall system design, commissioning, and handover must be led by a certified company.

Three-phase power: stepping up from single-phase domestic

If your background is primarily domestic, three-phase power is the single biggest technical step up in commercial and industrial work. It is not complex once you understand the fundamentals, but you need to be fully comfortable with the principles before you start designing and installing commercial distribution systems.

• Star vs delta: most commercial supplies arrive as three-phase four-wire star (415V line-to-line, 230V line-to-neutral). Delta configurations appear mainly in motor windings and some transformer arrangements. Understanding both is necessary for motor control work.
• Motor control: direct-on-line starters, star-delta starters, and variable speed drives (VSDs) are common in industrial and commercial plant. Each has different wiring requirements, overload protection, and fault consideration implications.
• MCCBs and industrial distribution boards: moulded case circuit breakers rated from 100A to 630A+ are the standard protective device for commercial distribution. Industrial distribution boards are designed around busbar systems rather than DIN rails. Understand discrimination, cascading, and fault level calculations before designing commercial distribution.
• Load balancing: unlike domestic work where you put everything on one phase, commercial distribution requires you to balance loads across all three phases to avoid neutral overloading and power quality issues. This is a design consideration, not just an installation one.
• Getting comfortable with 415V systems: safe working practices and appropriate PPE are non-negotiable. Commercial work at 415V with high prospective fault currents requires a different level of respect and precaution than domestic single-phase work.

Emergency lighting certification: design, installation and commissioning to BS 5266

Emergency lighting is one of the most accessible add-on packages for electricians moving into commercial work. Almost every commercial premises requires it, it can be quoted and delivered as a standalone contract, and it generates recurring revenue through annual inspection and testing programmes.

• Design to BS 5266-1: emergency lighting design requires a lux level calculation along all escape routes and open areas. Emergency luminaire positions must be specified to meet the minimum maintained illuminance requirements. Most manufacturers provide free design software that produces compliant layout drawings.
• Installation: self-contained maintained or non-maintained luminaires, central battery systems, or a combination. The choice depends on the premises type, client preference, and cost. Central battery systems are common in larger commercial buildings; self-contained fittings suit smaller premises.
• Commissioning and certification: on completion you issue an Emergency Lighting Commissioning Certificate covering all installed luminaires, their duration ratings (1-hour or 3-hour battery packs depending on premises classification), and the results of the full-duration discharge test.
• Annual inspection programmes: BS 5266 requires monthly flick tests, six-monthly partial duration tests, and annual full duration tests. Landlords, facilities managers, and building owners need someone to carry these out and maintain the log book. This is straightforward recurring revenue that builds long-term client relationships.
• NAPIT and NICEIC programmes: both bodies offer assessed emergency lighting installation and inspection categories. Adding these to your scope of approval gives clients the assurance they need when appointing you for commercial premises work.

Winning commercial contracts: how commercial clients buy

Commercial clients do not find electricians on Checkatrade. The procurement process is entirely different from domestic work and you need to understand it before you can navigate it successfully.

• Tender portals: large commercial clients, local authorities, NHS trusts, and housing associations advertise work on portals including Contracts Finder, Find a Tender (replacing OJEU post-Brexit), and private portals such as Proactis, Delta eSourcing, or Jaggaer. Registering on relevant portals and monitoring them consistently is the starting point for public sector work.
• Framework contracts: many large clients appoint a panel of approved contractors at the start of a framework period (typically two to four years) and then call off individual jobs against that framework without going back to competitive tender each time. Getting onto a framework is hard work upfront but produces a steady flow of work once secured.
• PQQ (pre-qualification questionnaire): before you are invited to tender, most commercial clients require you to complete a PQQ demonstrating your financial standing, insurances, accreditations, health and safety management, and relevant experience. Prepare standard answers and supporting documents — company accounts, insurance certificates, H&S policy, example EICs — so you can respond quickly when a PQQ lands.
• Accreditations they expect to see: NICEIC Approved Contractor or NAPIT Registered as a minimum. CHAS (Contractors Health and Safety Assessment Scheme), Constructionline, or equivalent supply chain management scheme membership. ISO 9001 quality management certification is increasingly expected on larger projects and frameworks. Some public sector clients also require SSIP (Safety Schemes in Procurement) recognition.

Commercial pricing: day rates, fixed-price tenders, and managing variations

Pricing commercial work incorrectly is the fastest route to losing money on a contract. The mechanisms and terminology are different from domestic work, and understanding them is not optional if you are going to tender competitively and profitably.

• Day rate vs fixed-price tender: day rate (or time-and-materials) work is straightforward — you charge an agreed rate for operatives plus materials at cost plus a margin. Fixed-price tendering requires you to take off a bill of quantities or a specification and price every element, carrying the risk if your takeoff is wrong or materials costs move. Most substantial commercial contracts are fixed price.
• Provisional sums: where scope is unclear at tender stage, the tender documents include provisional sums — estimated allowances for undefined work. When that work is instructed, it is priced and valued separately. Know the difference between defined and undefined provisional sums under JCT and NEC contracts, as the risk allocation differs.
• Schedule of rates: some clients operate a schedule of rates — a pre-agreed price list for defined tasks (first fix socket, second fix socket, 6A breaker installation, etc.) against which work is instructed and valued. Negotiating a schedule of rates that covers your actual costs plus margin is a skill in itself.
• Daywork variations: when instructed to carry out work that cannot be valued by any other method, daywork rates apply. Most contracts specify daywork rates at tender stage. Ensure your daywork rates cover all costs including plant, supervision, and overhead contribution — not just operative labour.
• Retention: a 5% retention is standard on most commercial contracts, reducing to 2.5% at practical completion and releasing the balance at the end of the defects liability period (typically 12 months). Chase retention release actively — it is your money and clients will hold it indefinitely if you do not pursue it.

Managing commercial projects: working with main contractors

On most commercial projects you will be working as a subcontractor to a main contractor rather than dealing directly with the end client. This changes how you manage the job, how you communicate, and where your obligations lie.

• The main contractor is your client: your contract is with the main contractor, not the building owner or occupier. Variations must be instructed in writing by the main contractor. Do not carry out additional work on verbal instruction from the end client without written confirmation from the main contractor.
• Programme management: commercial projects run to a master programme. You will be allocated attendance windows for first fix, second fix, and commissioning. Missing your programme slots causes knock-on delays for other trades and exposes you to delay damages. Understand your programme obligations before you sign the subcontract.
• Coordination with other trades: mechanical, structural, and fit-out trades all share the same space. Containment routes need to be agreed early. Attend coordination meetings, maintain a drawing register, and raise RFIs (requests for information) promptly when design information is missing or contradictory.
• O&M manuals and handover documentation: commercial projects require a formal handover package including all test certificates, as-installed drawings, equipment data sheets, maintenance schedules, warranties, and operating instructions. The main contractor will not release your final payment or retention without a complete and accepted O&M submission. Build the time to compile this into your programme from day one.

Building a commercial client base: starting small and scaling up

Very few electricians walk straight from domestic work into a six-figure commercial contract. The practical path is to build commercial experience and references progressively, starting with clients and project types where the barrier to entry is lower.

• Start with smaller commercial clients: letting agents, small office occupiers, independent retailers, and small hospitality businesses typically make procurement decisions without a formal tender process. They buy on recommendation and relationship. A well-managed £5,000 retail lighting job gives you a commercial reference and an EIC for your portfolio.
• Build references deliberately: ask every commercial client for a written reference or case study. Photograph completed work. Collect EICs, O&M samples, and programme records. These become your evidence base for PQQs and tender submissions.
• Move into the main contractor supply chain: approach regional main contractors and fit-out specialists directly. Offer to quote on smaller packages. Many are struggling to find reliable electrical subcontractors at the £20,000–£100,000 project level. Once you have delivered one job cleanly, repeat work follows.
• Target recurring maintenance and testing contracts: EICR programmes for commercial landlords, emergency lighting inspection schedules, PAT testing contracts, and annual fixed wire testing for multi-site retailers all generate predictable recurring revenue. One facilities management company relationship can be worth more annually than a dozen one-off domestic rewires.
• Track which enquiries convert: as you grow your commercial client base, knowing which marketing channels, referral sources, and tender routes are actually producing profitable work lets you concentrate your time and money on what works. Most electricians have no idea where their best commercial jobs actually came from.