AEMO Data Reveals a Fundamental Shift as Batteries Overtake Coal in the NEM
Battery storage now rivals coal capacity in Australia's grid, reshaping price formation and catching gas generators offside.
South Australia's wholesale power price averaged A$104.10/MWh at last close (2026-08-30), the only NEM region showing material volatility while the rest of the east coast sat in a pricing rut.5 The state's reliance on intermittent renewables, paired with a thin local gas fleet, leaves it exposed whenever the wind drops, and it is the clearest signal of how the rest of the grid is changing.3
Grid-scale batteries and rooftop solar are driving that transformation. AEMO's CEO told Australian Energy Week on Thursday (2026-06-11) that consumer-owned generation, with rooftop panels on one in three homes, now exceeds the capacity of the remaining coal fleet, at times covering more than 60% of demand.2
That is a structural break. Quarterly data shows east coast wholesale electricity prices averaged $74/MWh in Q2 2026, down 47% year-on-year. East coast gas prices fell to their lowest since Q2 2021, averaging $9.08/GJ, driven by lower domestic demand for gas-fired generation.5
The mechanism runs through the daily price curve. Batteries are shifting energy into evening peaks while solar floods the middle of the day, compressing the spread. AEMO counts 2.8 GW of behind-the-meter batteries responding to price signals but not centrally dispatched — equivalent to the entire capacity of Eraring Power Station.1
Volatility suppression has consequences for traders. WattClarity analysis from June (2026-06-21) noted prices had been "largely subdued" for months, including through the 2025-26 peak season.3 That quiet has pushed some generators toward event-driven strategies, betting on outages and cold snaps rather than seasonal peaks.1
Those events still arrive. AEMO issued roughly 500 directions to over 5 GW of generation plant and suspended the entire NEM during a late-autumn cold snap, one of the most challenging periods the operator says it has faced.2 Extreme prices returned, but briefly.
The coal exit intensifies the pressure. Nearly 40% of the NEM's coal fleet has retired since market start, and the average age of remaining stations is 38 years.2 Each unscheduled outage at those ageing units gets absorbed by batteries and gas peakers, and the gas peakers are increasingly costly to run as data centre demand lifts their economics.4
Queensland shows how fast supply is scaling. Average wind generation in the state rose 80% to an all-time high of 842 MW.5 That growth rate is why AEMO's Integrated System Plan, informed by CSIRO's GenCost report, keeps centring its forward view on renewables, storage and transmission rather than new thermal capacity.5
CSIRO's latest GenCost report, released in July (2026-07-15), said batteries are now Australia's preferred technology for flexible generation. Gas-fired generation is being pushed into ever-narrower operating windows, purely for the highest peaks and emergency balancing. Three consecutive quarters of data show the same direction.4
Gas traders should watch Wallumbilla, where the benchmark price sat at A$11.40/GJ as of Sunday (2026-08-30). Domestic demand for gas-fired power will fall further as battery and wind capacity builds, but the residual gas call for reliability and data centres will be priced at scarcity, not at average.4
The first sustained heatwave of summer, when the ageing coal fleet and the new battery fleet must run flat out together, remains the unresolved test. That combination has not yet been stress-tested at scale.2