WA Power & Wastewater Rules: What the State Actually Sets
WA's solar export rules changed on 1 May 2026, introducing a new two-pathway model that didn't exist before. Wastewater runs through the Department of Health rather than a state environmental authority, with a precise 540 litre-a-day threshold deciding whether council can approve your system alone or the Chief Health Officer needs to sign off too. This article covers what the state and network operators actually set for power and wastewater, before your specific council's requirements layer on top.
WA's power rules have just changed, and its wastewater framework runs through a different state department entirely compared to the other states covered so far — Health, rather than an environmental regulator. Each is covered as its own section below.
Power: two networks, and a new export choice from May 2026
WA has two electricity network operators: Western Power covers the South West Interconnected System (SWIS) — Perth metro and the state's south-west — while Horizon Power covers remote WA, operating a series of smaller, isolated local grids rather than one connected network. Horizon Power's export limits vary town by town depending on each local grid's capacity, and can be considerably lower than Western Power's standard limit, occasionally zero where a specific grid can't absorb additional generation at all.
On the Western Power network, the rules changed on 1 May 2026: new and upgraded systems must now choose between two pathways — full export access, which requires the inverter to support remote disconnection capability and qualifies for the Distributed Energy Buyback Scheme (DEBS), or a fixed 1.5kW static export cap without that remote-disconnection requirement. Standard connections can now accommodate up to 30kVA of aggregate inverter capacity, though the generation and export limits underneath that aggregate figure still apply separately. Systems installed before 1 May 2026 aren't affected by the new pathway choice.
Wastewater: a precise 540 litre-a-day threshold to Department of Health approval
On-site wastewater systems in WA are regulated under the Health (Treatment of Sewage and Disposal of Effluent and Liquid Waste) Regulations 1974 — different legislation from every other state covered in this series, sitting under WA Health rather than an environment or local government act. All applications go to your local government first, but a specific, precise threshold decides who actually approves it: a single dwelling producing up to 540 litres of wastewater a day can be approved by local government alone; anything producing more than that, or any building that isn't a single dwelling, needs approval from the Chief Health Officer at the Department of Health as well. A separate trigger applies to ancillary dwellings (granny flats and similar): once the combined occupancy of the main dwelling and the ancillary dwelling exceeds 8 people, Department of Health approval is required regardless of the litre volume.
All on-site wastewater products need prior Department of Health approval before they can be installed anywhere in WA, certified against the relevant Australian Standard (AS 1546.1 for septic tanks, AS 1546.2 for composting toilets, AS 1546.3 for secondary treatment systems, AS 1546.4 for greywater systems). As with other states, it's an offence to occupy a dwelling or use the system before a Permit to Use is issued following final inspection.
An important disclaimer, worth taking seriously
The Western Power/Horizon Power network split, the new May 2026 export pathway choice, and the Department of Health's 540L and 8-person wastewater thresholds are all verifiable, state-wide facts. But your specific network operator's local grid capacity, your council's site and soil evaluation requirements, and whether a particular product currently holds Department of Health approval all depend on your specific circumstances. Confirm directly with your network operator and your local government before installing solar, going off-grid, or installing a wastewater system — our WA power & wastewater rules by council tool covers a growing number of them directly.
Frequently Asked Questions
What changed with WA solar export rules in 2026?
From 1 May 2026, Western Power introduced a two-pathway model for new and upgraded systems: full export access, which requires remote disconnection capability and qualifies for the Distributed Energy Buyback Scheme, or a fixed 1.5kW static export cap without that requirement. Systems installed before that date aren't affected.
Why do Horizon Power's export limits vary so much across WA?
Horizon Power operates a series of smaller, isolated local grids across remote WA rather than one connected network, so export limits vary town by town based on each grid's capacity, and can be considerably lower than Western Power's standard limit.
Do I need Department of Health approval for a septic system in WA?
It depends on volume and dwelling type. A single dwelling producing up to 540 litres of wastewater a day can be approved by local government alone; anything above that, or any non-single-dwelling building, needs Chief Health Officer approval from the Department of Health as well.
Does an ancillary dwelling (granny flat) trigger extra wastewater approval in WA?
Yes, based on occupancy rather than volume: once the combined occupancy of the main dwelling and the ancillary dwelling exceeds 8 people, Department of Health approval is required regardless of the litre threshold.
Can I use any septic system I like in WA?
No. All on-site wastewater products need prior Department of Health approval before installation, certified against the relevant Australian Standard for that system type, and a Permit to Use must be issued after final inspection before the dwelling can be occupied.