NEM battery revenues crumble as record renewables, 9 GW fleet outpace demand
Australian grid-scale battery revenues are collapsing under supply pressure, with wholesale prices down 47% and the fleet's own growth compounding the squeeze.
Average wholesale electricity prices in Australia's National Electricity Market fell 47% year-on-year to $74 per megawatt hour in the June quarter, the lowest level since 2020, according to the Australian Energy Market Operator's latest Quarterly Energy Dynamics report.5 That is the headline number from a quarter in which renewables supplied a record 42.1% of NEM generation, up from 37.1% a year earlier, while grid-scale battery capacity more than doubled to exceed 9 GW.5
The price collapse is the clearest evidence yet that the NEM's supply stack is now structurally outrunning demand growth. Coal generation fell 5% and gas-fired output dropped 30% to its lowest second-quarter level since 2003, even as wind generation rose 20%, grid-scale solar increased 12% and rooftop solar grew 6.9%.5 Those are not marginal shifts; they represent a fundamental repricing of the entire dispatch order.
For battery operators, the math is turning brutal. The fleet that has been crushing evening peaks is now starting to compete with itself, as WattClarity has documented in recent analysis of charge-bid behaviour.4 The fleet is bidding to charge right at the clearing price in three of the past four quarters, and that price keeps rising, meaning the same batteries that profit from price spreads are increasingly setting the floor on the charge side rather than capturing value on the discharge side.4
Intra-day volatility is compressing in some periods even as inter-day and event-driven volatility becomes more important, according to an industry presentation covered by WattClarity in early June (2026-06-03).2 That is a subtle but damaging shift for storage economics, because the battery revenue model depends on large, predictable daily spreads that are being arbitraged away by the very fleet built to capture them.
The cause is simple supply arithmetic. RenewEconomy reported in June (2026-06-09) that batteries and wind are crushing evening peak prices, with more pain to come for gas and coal generators.3 The modelling behind that assessment points to a base case of 50 GW of wind, 49 GW of solar and 45 GW of batteries plus about 10 GW of gas, a build-out that leaves little room for thermal generators to set prices during the demand peaks they have historically owned.1
Household batteries are adding to the pressure from the demand side. Residential battery capacity increased 41% to 3,283 MWh over the past year, according to AEMO.5 Sunwiz data shows 1.5 GWh of home batteries were installed in May (2026-05-31), a material decline from April, but an ongoing installation rate of around 1 GWh per month for the rest of the year appears a conservative assumption.3 That would still add 7 GWh of new distributed storage by year-end, further eroding the evening peak that utility-scale batteries and gas peakers have relied on for revenue.3
Victoria recorded the biggest price decline at 60%, followed by New South Wales (53%), Queensland (44%), Tasmania (39%) and South Australia (38%).5 The geographic spread matters because the most renewable-penetrated states are seeing the sharpest compression, which is where new battery capacity has concentrated.
There is a counterweight emerging, but it is not near-term. AEMO said 17 proposed data centre projects with a combined maximum connection capacity of 9 GW were progressing through the transmission connection process by the end of June.5 If those connect, they would add meaningful baseload demand and could tighten the supply-demand balance. But grid connection queues in Australia are long, and the projects are proposals, not commitments.
Western Australia, a separate market, added more than 1 GW of grid-scale battery capacity over the past year.5 The same dynamic is playing out there, with solar deployment outpacing demand growth and storage revenues under pressure from their own proliferation.
The watch item is whether the charge-bid pattern documented by WattClarity firms up or fades in the coming quarters.4 If the fleet keeps bidding to charge at the clearing price, it is effectively signalling that the marginal revenue from a full battery no longer justifies waiting for a better spread. That would confirm the market is reaching storage saturation levels well before the current build-out wave crests, with consequences for every generator whose business case depends on the evening peak.4 The data centre pipeline is the only visible demand-side offset, and it is years away.