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.
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Does that means 3 phase systems would actually be worthwhile there now?. I assume the previous limit of 15kw would have meant only 5kw per phase, pretty much useless for all but the most modest power users.
i also suspect it means that when someone upgrades their solar – instead of just a lot of existing usable systems going to the tip, it means all existing systems will. It certainly sounds like retaining and AC coupling old systems will significantly penalise you under these new rules?
How is 5kw per phase?
I’m doing 3 Phase 10Kw Hybrid Inverter on my new build. It makes no difference whether its single or three phase as the smart meter only measures NET imports.
3 Phase is needed for All Electric homes with EV Charging and AC, simply cannot meet the peak on single phase or face a lot of nuisance tripping.
It makes a big difference if you are trying to back up the house. My son had a 15kw 3 phase inverter (5 kw per phase) and his house was constantly tripping the inverter, he upgraded to a 30kw unit when he got his 50kwh battery installed and has had no issues since.
It sounds like you are not getting a 3 phase inverter, but a single phase inverter on one your phases. Which means you can only do partial house backup?.
If the sun goes behind a cloud we trip our 3p setup when the EV AC charging is on and the air con and a few others. We are currently moving and we are going to change to the Sigenergy DC charger.
Brad,
Yours is exactly the case which makes the loony low kW/phase on-grid inverter restrictions grossly unworkable. The Sigenergy solar-coupled DC EV charger beautifully circumvents that regulatory obstruction, providing 11 kW or 25 kW BEV charging, without consuming AC capacity. That leaves all AC inverter delivery for other loads, given sufficient rooftop solar to power it all.
Finn’s “Fill yer roof.” dictum never had more relevance. (Generation beats storage in the long haul.)
An article on such market offerings, highlighting how they enable more than derisory self-consumption, is much needed, as folk slowly realise the sovereign mobility benefits of BEVs.
Its good to see that the inverter limit is 30 kw total (and in house use is not limited) and the solar panels can then be maxed out too. Better and cheaper and more reliable to install resistive hot water systems, charge vehicles at home or have other high usage requirements (eg; older houses with difficult/expensive insulation issues). While batteries have their place, it is more economical to have larger solar arrays to fill batteries more easily rather than larger batteries with limited lifespans. My records show that even on our worst solar days we generate 1kwh of energy per kw of panels, and if we can store that energy as hot water directly during the day, or a smaller/cheaper 15kwh battery system that gets us through the night, then we can operate without needing the grid at all. If the supply charge goes too high then we are well placed to decline the connection. We now need all states to see the commonsense.
As previously propounded in comments on SQ blogs, this regulation update is long past due – nationwide. The dufus 10 kW single-phase limit is not even enough for a level-2 BEV charger and a 3.6 kW HWS element – there’s less than nothing left for the rest of the house loads!
Off-grid self-consumption was 58 kWh here yesterday, limited by loads, not generation or inverter capacity. It is unwise to continue to impose perverse curtailment on grid-connected prosumers, as one day they will wake up to the unfair energy enslavement, which only serves corporate rent seekers.
We are not in the last fossil fuel crisis, and not the worst. As the more intelligent amongst us grasp that BEVs + ample rooftop solar = mobility security, the transition-sabotaging inverter limits must be removed, or more will be forced off-grid, to be able to function.
N.B. At $2.40/L, an MG4 is FREE after 9 years of driving 15k km pa. An Atto1 is paid off by fuel savings in 6.7 yrs. No bowser queues, home charged.
Thanks Erik, I have been wondering when the fuel cost savings makes a BEV economical to purchase.
Bevan,
If you’re looking at a BYD Atto3, make sure you check out the new model, coming out with a fair bunch of improvements on the really quite good current model. (My sister does a lot of miles in one.)
In any brand, it’s worth comparing range & price. (The base model MG4, with LFP battery and 300 km highway range does four 65 km shopping trips before I have to let my rooftop solar top it up. More is only useful on long trips, and I prefer to fly. Test drive one – it’s fun.)
They’re price-comparable with ICE now, lower by year’s end, they say, so it’s saving from day one, about now.
But mobility security!: I’m just back from a couple of hours on an electric excavator, clearing 250m of farm track, for access for fencing work. It’s rooftop solar powered, so diesel needed only for tractor-towing the tandem trailer 1 km home to recharge – after another half day’s work tomorrow. We can dump costly fossil fuel dependency, stepwise – but late starters miss out on early savings.
Just curious if there were any chance existing Powerwall 3 owners could take advantage of a change like this. My understanding is that the 5, 10 & 11.04 kW Powerwalls are all the same hardware, it is just that during commissioning the maximum output is set and it gets burnt into the firmware. Once that is done, only Tesla can change it, and they won’t do so if it would result in an illegal installation.
If someone previously had a couple of 5kW units, which was the max allowed at the time, could they now potentially apply and get Tesla to reset them to 10 or 11.04 kW and be able to double their inverter output at no/little cost?
Theoretically 30kVa is allowed already if you can get Western power to approve it and the single phase 15kVa generation limit already applies. Size limits have not changed since last May which Solarquotes remain well out of date on in their articles, it not a 10kVa limit currently.
A lot of us have already put in 15kVa sytems in the last 12 months.
Its just some of the wording being cleared up and export limit changes/ etc.
In reality with the 15kVa generation limit its fairly pointless going above that on single phase.
Hi Darren,
We have thousands of pages and the bloke who did most towards creating, curating & maintaining them has recently died.
It’s been a death in our family which we’re still getting used to.
If you’d like to help then please write up a summary for us, I’ll be happy to get the page updated.
Cheers
Was not referring to old articles, but this one.
“single-phase homes are limited to 10 kVA”
Hi Darren. Thanks for the comment — a couple of different things are being mixed together here.
The 10 kVA single-phase / 15 kVA three-phase figures refer to the standard “basic embedded generation” connection pathway under Western Power’s connection rules. That’s the streamlined approval process most residential systems go through.
Larger systems can sometimes be approved, as you mention — for example 15 kVA or more on single phase — but that generally requires a case-by-case assessment by Western Power rather than the basic pathway.
So it’s not that larger systems are impossible; it’s that the default limits for the streamlined approval process are lower, which is what the article was referring to.
For reference, the figures in the article come from the original source – Western Power’s Basic Embedded Generation Connection Technical Requirements.
Incorrect for the last 12 months as per the listed document for all users on a standard large network connection – I don’t know why people can’t read it correctly.
Referencing single phase for simplicity. You can have a 10kW solar plus a 10kW Hybrid – Generation limit of 15kVa. So effectively a user with 5kVa solar is allowed a 10kVa hybrid or vice versa.
I was probably one if the first Western power clients to push thru a 15kVa combined system, and while they were still figuring out their process at the time it was done under the document you listed.
Yes going above 15kVa requires a special approval and maintains the generation limit of 15kVa – as per clause 4.3.2, and requires a case by case approval.
I glad that the new revision clears up the ambiguity in its size limits, but in reality it hasn’t changed much in that regard.