Single-phase power is standard in most UK homes, supplying 230 volts through a single live conductor and a neutral. It is fine for domestic loads like lighting, sockets, and small appliances. But when you move into industrial settings with heavy machinery, large motors, and high power demands, single-phase quickly becomes a bottleneck. Three-phase power is the solution.
How Three-Phase Power Works
Three-phase power uses three live conductors, each carrying an alternating current offset by 120 degrees from the others. This creates a more consistent power delivery that is ideal for running large motors smoothly and efficiently. Between any two live conductors you get 400 volts, while any single live to neutral still gives 230 volts for standard equipment.
The key advantage is power density. A three-phase supply can deliver significantly more power through the same size cable compared to single-phase. A 100-amp three-phase supply provides over 69kVA of capacity, whereas a 100-amp single-phase supply delivers just 23kVA. That difference is what makes three-phase essential for workshops, factories, and commercial kitchens.
When Do You Need Three-Phase?
- CNC machines and milling equipment with motors over 3kW
- Industrial compressors and welding equipment
- Large vehicle lifts in garages and workshops
- Commercial EV charging with multiple 22kW points
- Large-scale heating and ventilation systems
- Three-phase generators and UPS backup systems
Upgrading from Single to Three-Phase
Upgrading an existing property from single to three-phase supply is not always straightforward. It requires a new service head, upgraded meter, and a three-phase distribution board. The Distribution Network Operator must be involved, and in some cases the local substation may need reinforcement. Lead times can vary from a few weeks to several months depending on the local network capacity.
Expert Tip
Before applying for a three-phase upgrade, carry out a detailed load assessment. It is common for businesses to request more capacity than they actually need, which increases connection costs unnecessarily. We can help you calculate your true demand and right-size the upgrade.
At D3C Electrical, we have completed three-phase upgrades for workshops in Leicester, factories in Loughborough, and distribution centres in Hinckley. We manage the DNO application, install the new distribution equipment, and ensure every circuit is correctly protected and labelled before handover.