Single Phase vs Three Phase EV Charging: Which Do You Need?

New Zealand homes receive electricity as either single-phase or three-phase supply. The difference is simple: single-phase uses one active conductor, three-phase uses three. More conductors, more capacity.

Single-phase is the standard for most NZ homes: 230V, supporting EV charging up to about 7.4kW on a dedicated 32A circuit. That is ample for normal household life including an EV.

Three-phase delivers 400V across three actives and supports up to 22kW AC charging. It is more common on newer builds, rural properties, and homes with big workshops or large heating plant.

The practical difference:

The framing that matters: if the car is home overnight, a single-phase charger restores hundreds of kilometres of range while you sleep. Unless you routinely arrive home nearly empty and must leave full again within a couple of hours, the extra speed of three-phase goes unused.

Two quick checks:

Look at your switchboard. A single-phase main switch is one or two poles wide; a three-phase main switch is three poles wide. A three-phase board often also has groups of breakers arranged across phases.

Look at your meter. Three-phase meters are typically labelled across L1, L2 and L3.

Not sure? Any EWRB-registered electrician will confirm it in minutes during a charger site assessment, which a good installer does as part of quoting anyway.

Getting three-phase to a home that does not have it involves your local lines company and potentially new service cabling: real money and real lead time, quoted case by case.

Three-phase makes sense if:

• You drive very high daily kilometres and genuinely need fast top-ups at home
• You run two or more EVs that often need charging in the same window
• You already have three-phase for a workshop or other equipment, so the increment is just the charger
• Your EV's onboard charger actually accepts 11kW or 22kW AC (check the spec sheet)

Stick with single-phase if: your car is home overnight, your daily kilometres are normal, and the budget has better uses (like solar, which actually reduces your running costs).

A common and expensive misconception: a 22kW wall charger does not mean 22kW charging. For AC home charging, the bottleneck is the onboard charger built into the car.

Many popular EVs accept only single-phase AC at up to 7.4kW. Put them on a 22kW three-phase wall charger and they still charge at 7.4kW. (The BYD Atto 3 is a well-known example of a 7kW-limited onboard charger.) Other models accept 11kW three-phase, and only some accept the full 22kW.

Before paying for three-phase anything, read your car's AC charging specification. If the car maxes at 7.4kW, a three-phase charger buys you nothing today, though it may be justified as future-proofing if a second, faster-charging EV is on the horizon.

DC fast charging is a separate matter entirely: public DC chargers bypass the onboard charger, which is why the same car that AC-charges at 7.4kW can DC-charge many times faster on a road trip.