WattClarity Modelling Shows 19 GW Battery Buildout Erases Coal's Evening Peak Revenue
Dispatch analysis published Sunday finds doubled NEM battery capacity would displace up to 6 GW of coal during the 5-9pm window that currently drives generator profits.
WattClarity, drawing on AEMO dispatch SCADA data and RenewMap figures dated 4 September 2026 (2026-09-04), published analysis on Sunday (2026-09-06) concluding that some coal generation in Australia's National Electricity Market is "definitively doomed." The trigger is a doubling of battery capacity in the NEM, from 9.5 GW to 19.2 GW and from 21 GWh to 55 GWh, a scale at which the dispatch arithmetic no longer works in coal's favour.5
The evening peak, roughly 5 pm to 9 pm, has been coal's most profitable daily window. Lower solar output and rising household demand push wholesale prices up, and baseload generators earn the bulk of their daily revenue in those four hours. WattClarity's modelling found that if the enlarged battery fleet were deployed exclusively across that window, it would eliminate all gas demand and displace up to 6 GW of coal generation in that period. Zero-fuel-cost storage bidding into the same slot leaves coal with no economic argument.5
Australia's battery buildout has moved fast to get here. The country added 2 GW of utility-scale battery capacity during 2025, a 233 per cent increase on 2024, making it the world's third-largest utility battery market behind only China and the United States, according to Clean Energy Council data reported by RenewEconomy on 25 May 2026 (2026-05-25).1
Financial commitments point to further acceleration. Developers committed 4.3 GW and 13.5 GWh of new big battery capacity in 2025, worth $4.8 billion of investment, up 67 per cent on the prior year's level, the CEC data show. Three projects defined the pace: AGL Energy's 500 MW/1,000 MWh Liddell Battery in New South Wales; the 600 MW/1,600 MWh first stage of the Melbourne Renewable Energy Hub, developed jointly by Equis and the Victoria government's State Energy Corporation; and Akaysha Energy's 55 MW/298 MWh Ulinda Park battery near Millmerran in Queensland, which began trading on the NEM by December 2025.1
Retail prices are already moving to reflect the shift in generation economics. The Australian Energy Regulator's final default market offer, released in May 2026 (2026-05-25), set maximum retail prices on a path to cut household time-of-use bills by up to 10.7 per cent from July across South Australia, New South Wales and south-east Queensland. Small business standing offer prices faced a steeper reduction of up to 20.9 per cent. Victoria separately set a 5 per cent average household cut for 2026/27, worth $84 off annual bills. Renewables supplied 43 per cent of Australia's generation across 2025, up from 39 per cent in 2024.2
The Australian Energy Market Operator flagged on 24 August 2026 (2026-08-24) that a record 40 GW project pipeline was placing the country on a stronger reliability path. AEMO qualified that assessment, stressing that timely delivery and operational availability of those projects remained essential. A pipeline is not commissioned capacity.4
David Dixon, a senior analyst at Rystad, told OilPrice.com that "Australia won't stay at number three" in global battery rankings and that "we have never seen anything of this magnitude before."3
WattClarity's analysis does acknowledge where coal retains residual value. Drought constrains hydro supply, particularly in Tasmania. Wind generation drops unpredictably. Extreme heat can push demand above what any plausible near-term battery fleet can cover. Under those stress conditions, coal still clears the market. But that role is intermittent by nature, and the modelling indicates coal's financial model increasingly depends on the frequency of supply stress events rather than on reliable evening dispatching.5
South Australia spot power traded at A$55.27/MWh and Wallumbilla gas at A$10.50/GJ in Sunday's (2026-09-06) NEM session. Newcastle coal held at $138.25 a tonne as of Monday (2026-09-07). Neither price yet reflects a market structure where 19 GW of battery storage competes daily for the same evening window.5
The variable is construction pace. Committed capacity must be built, connected and made operational before it can reshape NEM dispatch. AEMO's reliability assessments hinge on developers meeting their project timelines, and any slippage extends the period in which coal generators earn at current rates. How cleanly developers move from financial close to commercial operation over the next three years is now the number coal operators need to track.4,5