Three-Phase Power: When Does Your Business Need It?

Most Suffolk homes and small businesses run happily on single-phase 230V electricity. But when your machinery demands more power than a single phase can deliver, three-phase becomes essential. Here is when you need it, what it costs, and how the upgrade works.

Single-Phase vs Three-Phase: The Basics

Single-phase supply delivers 230V through one live wire, with a maximum capacity of 60–100A (13.8–23kW). Three-phase delivers 400V through three live wires, with capacity up to 200–400A (138–276kW). For high-demand equipment — CNC machines, commercial ovens, car lifts, large compressors — three-phase is the only practical solution.

When Do You Need Three-Phase?

Consider upgrading if your business uses any of the following: industrial kitchen equipment over 10kW, vehicle lifts or ramp systems, welding equipment over 15kW, large air conditioning or heat pump systems, multiple EV rapid chargers (22kW+), or manufacturing machinery with three-phase motors. Suffolk's growing food production and logistics sectors are common three-phase customers.

The Upgrade Process

Upgrading to three-phase is not a simple fuse change — it requires UK Power Networks to install a new three-phase service head, meter, and distribution equipment. The process involves:

1. DNO Application — We submit a formal request to UK Power Networks with your maximum demand calculations and single-line diagrams.
2. Site Survey — UK Power Networks assesses transformer capacity, cable routes, and pavement dig requirements.
3. Quotation — If network reinforcement is needed (new cables or transformer upgrade), costs can range from £2,000 to £15,000+. If capacity exists nearby, the connection fee is £800–£2,500.
4. Installation — Once approved, we install a three-phase distribution board, balance your loads across the three phases, and certify to BS 7671.

Load Balancing

Simply having three phases is not enough — your electrical load must be balanced across all three to prevent neutral overload and voltage instability. ELECSI designs the distribution carefully, splitting high-demand circuits evenly. We provide load calculation spreadsheets showing phase balance before and after the upgrade.

Cost Summary

Typical costs for a Suffolk business: DNO connection fee £1,500–£5,000; three-phase distribution board and cabling £2,000–£4,000; internal circuit modifications £500–£2,000. Total upgrade: £4,000–£11,000. For businesses with heavy machinery, this pays for itself through equipment performance and reliability within 2–3 years.