Three-Phase Power Installation
Upgrade from single-phase to three-phase electricity supply. DNO application, new distribution board, and load balancing. Qualified and insured.
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Three-Phase Power Installation
Qualified electrician
Same-day service
Most jobs matched within hours.
Upfront pricing
Clear quotes before work starts.
Qualified pros
NICEIC & NAPIT registered.
Pay when done
Funds held until you're happy.
How it works
Load assessment and feasibility
The electrician calculates your current and projected electrical demand, confirms that a three-phase upgrade is the right solution, and checks the feasibility with your DNO. In some areas, three-phase supply is readily available at the boundary; in others, significant cable work may be needed.
DNO application
A formal application is submitted to your Distribution Network Operator (UK Power Networks, Western Power, Scottish Power, etc.) for a three-phase supply. The DNO will survey the site and provide a quotation for the connection work. Lead times are typically 6-12 weeks.
DNO connection work
The DNO installs the three-phase service cable from the street to your property, fits a new three-phase cut-out and meter, and provides the earthing arrangement. This work is carried out by the DNO (or their appointed contractor) and is included in their quotation.
Three-phase distribution board installation
Your electrician installs a new three-phase consumer unit or distribution board. Circuits are balanced across the three phases to distribute the load evenly. High-load single-phase circuits (EV charger, heat pump, cooker) are allocated to different phases. Any three-phase equipment is connected directly.
Testing, certification, and commissioning
The complete installation is tested to BS 7671 standards, including phase rotation, voltage balance, earth fault loop impedance on all phases, and RCD trip times. An Electrical Installation Certificate is issued and the work is notified to Building Control. The electrician verifies load balance across all three phases.
What's included
What's involved
A three-phase installation upgrades your property from a standard single-phase supply (230V, typically 80-100A) to a three-phase supply (400V, typically 3x100A), tripling your available electrical capacity. This is needed when the electrical demand of a property exceeds what a single-phase supply can provide — common in large residential properties with multiple high-load circuits (EV chargers, heat pumps, electric heating), commercial premises, workshops, and properties with three-phase machinery. The upgrade involves applying to your Distribution Network Operator (DNO), installing a new three-phase meter and consumer unit, and redistributing circuits across the three phases.
A standard single-phase supply provides approximately 23kW (100A at 230V). Modern electrical demands — EV chargers (7kW), heat pumps (3-5kW), induction hobs (7kW), electric showers (9-10kW) — can easily exceed this, especially if multiple loads run simultaneously. Symptoms of an inadequate supply include the main fuse blowing, lights dimming when heavy loads switch on, and the DNO refusing permission for additional high-load installations. A three-phase upgrade provides approximately 69kW (3x100A at 230V), giving ample headroom for current and future electrical needs.
Get a personalised quote
Typical cost: £2,000–£6,000per installation
Every job is different — pricing depends on your property, location, and specific requirements. Describe what you need and a qualified electrician will quote you directly.
How long does it take?
The electrician's work (distribution board, circuits, testing) typically takes 1-3 days. However, the overall project timeline is 8-16 weeks due to the DNO application and connection lead time. Allow 6-12 weeks for the DNO process alone.
Regulations & safety
Safety notice
Three-phase electricity at 400V between phases is significantly more dangerous than single-phase 230V. All three-phase work must be carried out by a qualified electrician experienced with three-phase systems. Never attempt to work on three-phase equipment yourself.
During the changeover from single-phase to three-phase, the property will be without power for a period. The DNO disconnection and reconnection may take a full day. Plan accordingly for essential services.
Three-phase systems require careful load balancing. An unbalanced system causes excessive neutral current, voltage imbalances, and can damage sensitive equipment. Your electrician must design the circuit allocation to distribute loads evenly across all three phases.
BS 7671:2018+A2:2022 (IET Wiring Regulations, 18th Edition)
Governs the design and installation of the three-phase distribution system, including circuit protection, cable sizing, earthing, and the requirement for phase balance and neutral sizing.
Electricity Safety, Quality and Continuity Regulations 2002 (ESQCR)
Governs the connection between the DNO supply and your installation. The DNO is responsible for providing the three-phase supply up to and including the meter. Your electrician is responsible for everything after the meter.
Part P of the Building Regulations (Approved Document P)
The installation of a new three-phase distribution board and associated circuits is notifiable electrical work. It must be carried out by a registered electrician.
Distribution Network Operator (DNO) Connection Standards
Each DNO has specific requirements for three-phase connections, including the position of the cut-out, meter, and earthing arrangement. Your electrician coordinates with the DNO to ensure compliance.
What to expect
Having issues with your existing installation?
Already have a three-phase power and having issues? Check our troubleshooting guides.
Frequently asked questions
How do I know if I need three-phase?
How much does the DNO charge for a three-phase connection?
Can I keep my existing circuits when upgrading to three-phase?
Do I need planning permission for a three-phase upgrade?
What is the running cost difference between single and three-phase?
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