Single-phase vs three-phase power: what is the difference and when do you need three-phase?

Short answer: Single-phase power uses one phase and a neutral at 230 V; most homes are single-phase. Three-phase power has three phases with 400 V between them and carries about three times the power at the same current. Workshop machines, lifts, heat pumps, large air conditioners and 11–22 kW EV charging need three-phase. A single-phase home can charge at up to 7.4 kW (32 A).

Calculating power

• Single-phase: Power = 230 V × current. 16 A ≈ 3.7 kW, 32 A ≈ 7.4 kW.
• Three-phase: Power = √3 × 400 V × current (≈ 3 × 230 V × current). 16 A ≈ 11 kW, 32 A ≈ 22 kW.

Because three-phase carries the same power at lower current, cables stay thinner and voltage drop is lower. Motors also run more smoothly and efficiently on three-phase.

Wire colours

Under the current IEC standard: L1 brown, L2 black, L3 grey; neutral blue; protective earth green-yellow. A single-phase circuit has a brown phase, blue neutral and green-yellow earth. Older buildings may use other colours, so always measure before working.

Single-phase and three-phase EV charging

• Single-phase 32 A: 7.4 kW. Charges a 60 kWh battery from 20% to 80% in about 5–6 hours.
• Three-phase 16 A: 11 kW. The same charge takes about 3.5 hours.
• Three-phase 32 A: 22 kW. Only helps cars that accept 22 kW AC; most cars are limited to 11 kW on AC.

If a car charges on one phase only, it will do so even on a three-phase charger. Check the car's AC charging power first, then the home's supply.

Upgrading a home to three-phase

A three-phase connection is requested from the distribution company (UEDAŞ in Bursa). The meter, main fuse and building riser may need replacing; in apartment blocks the riser capacity is checked. After the upgrade, single-phase circuits in the home are spread evenly across the three phases.

Phase balance

In a three-phase building, loads must be spread evenly across the phases. An overloaded phase trips its fuse, the neutral carries excess current and voltages become unbalanced. When adding large loads such as an EV charger, the consumer unit is rebalanced.

Which do I need?

• Flat, normal household use, charging up to 7.4 kW: single-phase is enough.
• Detached house, heat pump, large air conditioning, 11 kW charging, more than one car: three-phase.
• Workshops, businesses, shared car parks: three-phase.

In Bursa, ENGN provides electrical installation, three-phase consumer units and EV charger installation.

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