NEM Coal Faces Evening Profit Wipeout as Battery Fleet Nears 19 GW
ITK analysis of AEMO dispatch data projects the incoming battery build-out would eliminate up to 6 GW of coal and all gas demand in the NEM's peak hours.
Analysis published Sunday (2026-09-06), drawing on AEMO dispatch SCADA data and RenewMap figures from September 4, 2026, concluded that coal generators in Australia's National Electricity Market face a straightforward arithmetic problem: once 19.2 GW and 55 GWh of utility-scale batteries are operating across the grid, their profits will be wiped out. The ITK estimate covers a build-out already under way. Battery capacity in the NEM is moving from 9.5 GW to 19.2 GW in power terms, and from 21 GWh to 55 GWh in stored energy.5
The price signal reinforces the projection. NEM-wide wholesale spot prices averaged A$74/MWh in the second quarter of 2026, down A$66/MWh, or 47%, from the same quarter a year earlier, according to Australian electricity and gas markets data published in August 2026. East coast wholesale gas prices averaged A$9.08 per gigajoule in Q2 2026, the lowest quarterly average since the second quarter of 2021, driven by lower domestic demand. On Wednesday (2026-09-09), Wallumbilla gas was at A$11.12/GJ and the South Australia spot market sat at A$82.99/MWh.4
The most exposed window is the 5 pm-to-9 pm evening peak. The ITK analysis estimates that a fully deployed battery fleet of this scale, if concentrated in those hours, would eliminate all gas-fired generation and up to 6 GW of coal demand. That is where thermal generators have historically earned the margins that sustain their fixed costs. Once that revenue stream closes, the case for keeping aging plant online collapses.5
The coal fleet is poorly positioned to absorb the pressure. Nearly 40% of NEM coal capacity has retired since the market was established, and the average age of the stations still running is 38 years, the AEMO chief executive told Australian Energy Week on June 11, 2026. Consumer rooftop solar is compressing margins from the daytime side: more than 4 million installations across one in every three Australian homes have pushed consumer generation capacity above the capacity of the remaining coal fleet, at times meeting more than 60% of all NEM demand.2
Behind-the-meter batteries add to the squeeze from a less visible direction. AEMO reported 2.8 GW of unscheduled, price-responsive behind-the-meter battery capacity in the NEM — roughly equivalent to the full output of Eraring power station. These units respond to market prices without appearing in the central dispatch stack, compressing price spikes without the visibility that centrally dispatched plant provides.1
Rising data centre demand runs against the trend. CSIRO's GenCost 2026 annual report, released in July 2026, found data centres are pushing up the cost of gas-fired generation in Australia, reinforcing batteries as the preferred technology for new flexible capacity. But data centre load also adds evening demand that the incoming battery fleet will need to serve as well as offset.3
Queensland's wind output sharpened the midday surplus. Average wind generation in the state rose 80% in Q2 2026 to a new all-time high of 842 MW, the August 2026 markets update showed. That volume of wind during daylight hours pushes down midday prices and creates low-cost charging windows for batteries before the afternoon trough.4
South Australia stands apart. It was the only NEM region with material price volatility in Q2 2026, and its spot market was at A$82.99/MWh on Wednesday (2026-09-09), above the NEM-wide Q2 average of A$74/MWh. Higher renewable penetration and thinner interconnection leave the state exposed to intra-day swings regardless of battery deployment elsewhere in the grid.4
The ITK analysis notes conditions that could give coal temporary reprieve: drought cutting Tasmanian hydro, prolonged wind lulls, or a sustained heat event could restore thermal dispatch even with 19 GW of storage in service. Those are weather variables, not a commercial case. Battery grid connection approvals and NEM dispatch rules for storage are the two variables that will pace coal's exit from the evening peak.5