Guide to Single-Phase and 3-Phase Electricity Supplies

What is a Single-Phase Electricity Supply?

Single-phase electricity is the standard power supply for most UK homes, delivering 230 volts via two wires (a live and a neutral). It’s typically used in properties with average consumption, such as homes with gas central heating, lighting, and standard appliances.

• Mostly used in – Homes and small businesses
• Typical capacity – Up to 20 kVA
• Best suited for – Lighting, plug sockets, small appliances, low-demand heating

In layman’s terms, you can think of single-phase supplies being like a cyclist pedalling, power is delivered in bursts with small dips in between.

What is a 3-phase electricity supply?

3-phase electricity is usually found in commercial, industrial, or large residential properties where demand is higher. It uses three live wires plus a neutral, each delivering peak power at different times for a more stable flow.

• Common in: Large homes, blocks of flats, businesses, industrial sites
• Typical capacity: 20–100+ kVA
• Best suited for: High-power machinery, lifts, electric motors, EV chargers, larger HVAC systems

In layman’s terms, you can think of 3-phase supplies like three cyclists on a tandem bike, each pedalling at different times so there’s always smooth, continuous power with no dips.

Feature	Single-phase	3-phase
Voltage (UK)	230V phase-to-neutral	400V between phases
Power capacity	Up to 20 kVA	20-100+ kVA
Power delivery	Fluctuates with peaks and dips in supply	Continuous, smoother power delivery as phases peak at different times
Efficiency	Less efficient for heavy loads (higher resistive losses & voltage drops)	More efficient for heavy loads (balanced across three conductors, lower current per wire)
Motor performance	Can cause vibrations, lower torque; often needs auxiliary motor start-up kit	Smooth, stable, higher torque motor performance with greater efficiency
Common usage	Homes & small businesses (lighting, appliances, heating)	Larger homes, commercial & industrial sites, data centres, high-demand equipment
Installation cost	Lower (simpler wiring & single-phase meter)	Higher (extra wiring, 3-phase meter, possible network upgrades or groundwork)

Pros and cons of single-phase

Pros of single-phase

• Ideal for standard home and office use
• Simpler and cheaper to install
• Widely available across the UK

Cons of single-phase

• Limited capacity for heavy loads
• Can experience dips in supply
• Less efficient for large motors or machinery

Pros and cons of 3-phase

Pros of 3-phase

• Provides higher, more stable capacity
• Better for industrial and commercial equipment
• More efficient distribution with lower losses
• Supports faster EV charging and heavy-duty systems

Cons of 3-phase

• Higher installation cost
• Less common in standard homes
• More complex to manage and maintain

Which supply do I need?

• Most UK homes – Single-phase is sufficient.
• Larger homes, developments, or properties with high-demand equipment (e.g. lifts, large motors, EV charging infrastructure) – 3-phase is recommended.

Not sure? – The easiest way to check is by looking at your main fuse/service head:

• One fuse = single-phase
• Three fuses = 3-phase