Three-phase power and solar in Perth: what you need to know

Most Perth homes have single-phase power — one live conductor bringing 230V to the switchboard. A minority of homes (typically those built before the 1980s in older suburbs, some large modern homes, and properties with heavy equipment loads) have three-phase power — three live conductors, each at 230V, giving access to 400V three-phase supply.

Whether your home is single-phase or three-phase affects what solar inverter you can install, how large a system you can connect, and how Western Power calculates your export limit.

How to check if your home is three-phase

Look at your switchboard. A single-phase home typically has one main switch (two poles: active + neutral). A three-phase home has a three-pole main switch.

You can also check your Western Power connection documents or call Western Power to confirm.

Why three-phase matters for solar

Inverter compatibility

Single-phase inverters connect to one phase of your supply. They can be installed on a three-phase home but the output goes to one phase only — other phases still draw from the grid independently.

This creates a potential issue: if you have a large single-phase solar inverter on one phase, that phase receives solar credits, but appliances on the other two phases continue to import from the grid regardless. Your electricity meter may offset exports against imports differently depending on your metering setup.

Three-phase inverters balance load across all three phases, avoiding this asymmetry. For a three-phase home, a three-phase inverter is almost always the correct choice if the system is large enough to justify it.

System size

For residential systems above approximately 10kW, Western Power generally requires three-phase connection for the inverter. This is both a technical requirement (single-phase systems can cause voltage imbalance at higher outputs) and a grid management consideration.

If your single-phase home wants a system larger than 10kW, you may need a three-phase upgrade — or split the system across multiple single-phase inverters on different phases.

Export limits

Standard residential export limits apply per-phase:

• Single-phase: 5kW export (standard uncontrolled, some suburbs 3kW)
• Three-phase: 5kW per phase = 15kW total export capability (standard)

A three-phase connection gives significantly more export headroom for large systems, which is relevant if you're installing a 13kW+ array and want full export capability.

System size guidelines

| Household type | Recommended system size | Phase requirement | |---|---|---| | Small home, 1–2 people | Up to 6.6kW | Single-phase OK | | Medium home, family | 6.6–10kW | Single-phase OK | | Large home, pool, EV | 10–13.3kW | Three-phase recommended | | Large home + battery + EV | 13.3kW+ | Three-phase required | | Small business | Varies | Often three-phase |

Three-phase inverter brands in Perth (2026)

Fronius Symo (3–15kW): Three-phase string inverter, widely used in Perth for large residential and small commercial systems. Also available as Symo GEN24 Plus (hybrid, battery-ready). Excellent monitoring via Solar.web.

Sungrow SG series (5–30kW): Competitive pricing at three-phase range. SG8/10/15kW used on large Perth homes. iSolarCloud monitoring. Native pairing with Sungrow SBH three-phase battery inverter.

SolarEdge SE series (5–17kW three-phase): Three-phase with power optimisers per panel. Good for shade and monitoring scenarios. SE home hub (three-phase version) available for battery integration.

SMA Sunny Tripower: Industry-standard three-phase string inverter. Less common in new Perth residential installations than Fronius/Sungrow but widely serviced.

Battery storage with three-phase

Most common residential batteries in Perth (BYD Battery-Box, Sungrow SBR, Powerwall 2) are designed to work with single-phase supply. When adding battery storage to a three-phase home:

AC-coupled battery (e.g. Powerwall 2): Connects to one phase of the three-phase supply. Backup circuits during an outage are typically limited to that single phase. The other two phases lose power in a grid outage even with a Powerwall.

DC-coupled via three-phase hybrid inverter: Some three-phase hybrid inverters (e.g. Fronius Symo GEN24 Plus) can DC-couple a battery and provide backup across all three phases during a grid outage. This is a more capable solution for three-phase homes but more complex and expensive.

If whole-home backup across all three phases is important to you, confirm with your installer exactly which phases are backed up in your proposed design.

Upgrading a single-phase home to three-phase

If you have a single-phase home but want a large solar system (10kW+), adding a three-phase service connection from Western Power is possible but costly:

• Western Power application and connection fee
• New switchboard (three-phase main switch and wiring)
• Internal re-wiring if required

Total cost: approximately $3,000–8,000+ depending on distance to the street and switchboard condition.

For most large residential solar systems, installers find a way to work within single-phase limits (multiple smaller inverters on split phases, or accepting the 10kW single-phase ceiling) rather than recommending a three-phase upgrade.

Western Power connection standards and export limits are subject to change. Confirm current requirements with your installer before specifying system size.