AEMO Sees Western Australian Battery Fleet Quadrupling as Home Storage Reshapes Grid Peaks
Distributed battery capacity in WA's main grid is forecast to grow from 550 MW to 2.3 GW by 2035-36, cutting grid investment needs and weakening the case for coal peaking capacity.
Australia's energy market operator released a 10-year grid outlook on Tuesday (2026-06-23) projecting home batteries will fundamentally alter how Western Australia's South West Interconnected System handles its daily demand cycle, with distributed storage capacity set to grow from around 550 megawatts in 2026-27 to approximately 2,300 megawatts by 2035-36.3
AEMO's 2026 Electricity Statement of Opportunities for the WA market shows rooftop solar capacity in the SWIS also forecast to nearly double from current levels. Taken together, those two trends are expected to flatten the solar duck curve — the steep evening demand ramp that emerges as rooftop generation fades — which has historically driven the case for retaining gas and coal peaking capacity in the state.3
WA state government energy policy lead Jai Thomas called the finding the "absolute banger of a highlight" from the report. AEMO projects that around 640 megawatts of batteries will be enrolled in virtual power plant arrangements by 2028-29, at which point VPP coordination alone is expected to reduce the need for new grid-scale investment by approximately 200 megawatts.3
That VPP buildout has to come from a low base. Across Australia, fewer than 10 percent of battery owners have joined a VPP scheme, even as the national rooftop solar fleet now spans more than 4.3 million homes and Queensland alone accounts for 1.16 million installations.2 The gap between installed distributed capacity and actively dispatched capacity is the central uncertainty in the AEMO projection.
In the NEM — Australia's eastern and southern grid, which operates separately from the WA market — the distributed battery stock is already substantial. WattClarity data showed AEMO tracking 2.8 gigawatts of behind-the-meter batteries responding to prices but not centrally dispatched, a combined output equivalent to Eraring Power Station in New South Wales.1 Those batteries tend to compress intraday price volatility while leaving event-driven spikes intact. South Australia day-ahead spot power stood at $491 per megawatt hour on Tuesday (2026-06-23), reflecting ongoing demand tightness in a state that draws heavily on Victorian interconnector flows during peak periods.
The WA outlook rests on a participation assumption that has yet to materialise at scale. Consumer batteries are counted on to do significant grid work, but enrolment in VPP schemes enabling coordinated dispatch remains far below what the projections require. Battery owners may respond passively to time-of-use price signals without formally enrolling — which partly explains how the NEM's 2.8-gigawatt unregistered fleet emerged — but passive response is less reliable during a grid stress event than a registered virtual plant with a defined dispatch obligation.1,2
Rising overall consumption adds a counter-pressure. AEMO's WA projections account for growing demand even as peak demand falls; the net result is a grid that still requires significant investment, just in different technologies and locations.3
For power market participants, the critical data series is WA VPP enrolment through 2027-28. If participation approaches the 640-megawatt threshold ahead of schedule, the implied reduction in peaking capacity procurement alters the shape of WA's reserve capacity target and changes the value of gas peakers holding capacity contracts in that window. Enrolment stalling at current levels would push the grid investment deferral back onto conventional plant, and leave the coal exit timeline dependent on direct policy action rather than market displacement.3