WA’s Big Change To Inverter Rules Kicks Off In May

Western Australia is updating the technical rules for small-scale solar and battery systems, with a new generous inverter size limit to be introduced from 1 May 2026.

How Are WA Rules For Solar And Batteries Changing?

If you already have solar, nothing changes — unless you upgrade. But if you’re installing a new system, or adding a battery or extra inverter capacity after that date, your setup will need to comply.

Importantly, these changes apply only to systems connected to the South West Interconnected System (SWIS) — the main grid covering Perth and most of WA’s population and operated by Western Power. They don’t apply to Horizon Power networks in regional and remote WA.

Larger Systems Allowed Under One Combined Cap

From May 2026, homes and small businesses on the SWIS can install up to 30 kVA of total inverter capacity under a standard connection.

That 30 kVA refers to the combined rating of all inverters on the property — solar and battery added together. It’s not about panel size or battery storage; it’s about total inverter output.

Under current Western Power rules, solar and battery inverters have effectively been treated separately. A home could install a 10 kW solar inverter and later add a 10 kW battery inverter without those ratings being assessed as a single limit.

From May 2026, all inverter capacity on site will count toward one 30 kVA aggregate cap.

So a 10 kVA solar inverter, 10 kVA battery inverter and 5 kVA additional inverter would total 25 kVA — within the new limit.

Single Phase Gets a Big Boost

The same 30 kVA cap applies to both single-phase and three-phase connections.

Currently, single-phase homes are limited to 10 kVA, while three-phase sites are allowed 15 kVA. The new framework gives single-phase households the same inverter headroom as three-phase properties — flexibility not currently seen in other states.

Export Control Becomes Mandatory

From 1 May 2026, all new or upgraded systems on the SWIS must include either:

• Remote disconnect and reconnect capability (controlled by the retailer), or
• A fixed export limit of 1.5 kW.

If remote capability is enabled — usually via the inverter’s internet connection — exports can be managed during network events. Without it, the system defaults to the 1.5 kW export cap.

Updated Technical Standards

All inverters installed from May 2026 must comply with the grid connection standard AS/NZS 4777.2:2020 and be configured to the Australia Region B grid profile. Installers must also follow updated commissioning and compliance documentation requirements under Western Power’s procedures.

How WA Compares

Across the east coast, single-phase households are typically limited to 5–10 kVA inverter capacity, with export caps often around 5 kW. WA has sometimes carried the old “Wait Awhile” nickname — but this time it might have been worth the wait.

The new 30 kVA aggregate allowance is generous on inverter sizing, particularly for single-phase homes, even if the default 1.5 kW export fallback is lower than some east-coast limits. In short: bigger systems are allowed, but exports remain tightly managed.

Why The Change To Solar Rules In WA?

WA has some of the highest rooftop solar penetration in the world. On mild, sunny days, minimum demand on the SWIS can fall extremely low, creating grid stability challenges. These updates aim to keep solar and battery growth moving while giving the network tools to manage system security when needed.

If you’re getting quotes now for installation after 1 May 2026, your installer should already be designing to these requirements. Bear in mind there is a massive rush for batteries before the rebate goes up in May, so with installers under the pump there could be a chance your scheduled April install gets pushed back.

For more information for customers, read the WA government’s explainer, while installers have their own explainer.

For current grid connection rules in WA including Western Power (south-west WA) or Horizon Power (rest of WA) distribution area see SolarQuotes processes and rules guide here.