For months, one of the world’s largest grid batteries ran at half power — a single transformer carrying the load while engineers worked to bring the rest of the system back. Now, with a second transformer back online, the Waratah Super Battery has climbed to 700MW of operational capacity, recovering 82% of its full 850MW potential.
Built to help stabilize Australia’s National Electricity Market, the BlackRock-backed facility in New South Wales stores 1,680MWh of energy — enough to rank among the largest battery installations on the planet. This latest milestone marks a turning point in a commissioning process that proved far more difficult than planned.
A battery built to anchor the grid
The Waratah Super Battery was never designed to be a passive asset. Rated at 850MW and 1,680MWh, it was contracted to Transgrid under the System Integrity Protection Scheme — a mechanism within Australia’s National Electricity Market that deploys large-scale resources to protect grid stability during major network disturbances. SIPS-contracted assets must respond rapidly and reliably, which means the battery’s availability is not purely a commercial question. It is a grid security question.
Developer Akaysha Energy, backed by BlackRock, positioned Waratah as a cornerstone of New South Wales’ energy transition — a facility capable of absorbing and dispatching energy at a size that meaningfully shifts the needle for the NEM. At this scale, the project ranks among the largest battery installations anywhere in the world.
That strategic ambition made the events of late 2025 all the more significant.
When the transformers failed
In October 2025, High Voltage Transformer 3 suffered a catastrophic internal fault. The failure caused winding damage and an overpressure event, rendering the transformer beyond repair — and it happened just hours before the facility was due to complete its next commissioning milestone, a particularly painful piece of timing.
Engineers then took HVT2 offline as a precautionary measure. With one transformer destroyed, continuing to operate a second without full investigation carried unacceptable risk. The consequence was stark: the facility dropped to 350MW, running on a single transformer and meeting only its interim SIPS obligation.
The commercial impact was immediate. Because the SIPS contract includes mechanisms to adjust payments based on actual service provided, Akaysha was receiving roughly half of its expected contracted revenues during this period. A project of this scale, with significant capital behind it, was effectively idling while the repair process got underway.
The recovery: one transformer at a time
Akaysha did not treat both transformers as a single problem. HVT2’s remediation was incorporated into a separate, defined program of work — one that finished ahead of schedule. That sequencing mattered, allowing HVT2 to return to service independently without waiting for the longer HVT3 replacement timeline.
The HVT3 replacement process moved through a design review involving Wilson Transformer Company and independent consultants. Akaysha and its contractor, Consolidated Power Projects Australia, selected Wilson — an Australian manufacturer — deliberately. The choice enabled rapid engineering engagement and faster mobilization of manufacturing resources than an overseas supplier could have readily matched, along with a strong on-site presence throughout the process.
The replacement transformer remains on track for delivery to site in the third quarter of 2026. Full 850MW capacity is targeted by the end of the year.
What 700MW means for revenue and the market
With HVT2 back online, the 700MW now available is split into two distinct streams. The first 350MW continues to fulfill Waratah’s contracted SIPS obligations with Transgrid. The second 350MW is deployed on a merchant basis into the NEM, participating in wholesale energy markets and ancillary services.
Restoring the contracted income stream closes the revenue gap from the commissioning period, but merchant participation opens a separate opportunity — one shaped by how NEM economics have shifted over the past year. Battery storage revenues across the NEM have grown substantially as the installed fleet has expanded.
CleanCo Queensland’s 250MW Swanbank BESS earned AU$743,000 in a single month of dispatch revenue. Average two-hour intraday spreads across all NEM states fell below AU$106/MWh in May 2026 as the battery fleet absorbed midday solar surplus at increasing scale. The market is becoming more competitive, but it remains active and consequential for a facility of Waratah’s size.
The road to 850MW — and beyond
The final step is straightforward in description, if not in execution: deliver HVT3, install it, commission it. Once operational, the full 700MW SIPS service will be available to Transgrid, and the remaining 150MW of power capacity above that threshold will also enter merchant market participation.
Akaysha’s broader portfolio is expanding in parallel. BlackRock is reported to be considering raising several hundred million dollars for Akaysha at a valuation above US$1 billion, with potential investors described as being in early-stage discussions. Waratah’s recovery — however difficult — strengthens that case.
The project carries a broader lesson for the industry. Transformer supply constraints and grid integration complexity are not unique to Waratah — large-scale BESS commissioning globally faces similar risks. The decision to engage a domestic manufacturer to accelerate engineering response is a data point other developers will note. As more gigawatt-scale batteries enter the commissioning queue worldwide, how quickly HVT3 comes online will be watched closely.
Carlos is an engineer with strong expertise in technical and industrial topics. He previously worked at international companies such as Siemens and speaks Spanish, German, English, and Italian.
