The Hunter Renewable Energy Zone has its first major project under construction: a 400 MW solar farm paired with a 200 MW/400 MWh battery on the site of the closed Muswellbrook coal mine, developed by Swedish utility OX2. This marks the physical start of NSW’s most symbolically charged energy transition corridor, where rehabilitated mining land and existing grid infrastructure are being repurposed for utility-scale renewables and storage at a scale that can materially replace retiring coal generation.
Hunter REZ moves from declaration to steel in the ground
The Hunter REZ was formally declared in December 2023 as the third of NSW’s five legislated Renewable Energy Zones, following the Central-West Orana and New England zones. Unlike its predecessors, the Hunter carries unique political and economic weight: it sits atop the state’s historic coal heartland, encompasses the Eraring and Bayswater power station catchments, and its 7.5 GW intended capacity is explicitly designed to absorb generation displaced by the scheduled 2025-2028 retirements of Origin’s Eraring (2.88 GW) and AGL’s Bayswater (2.64 GW). The OX2 Muswellbrook project – 400 MW solar plus a two-hour battery – is the first to reach financial close and commence construction within the REZ framework, accessing the dedicated transmission upgrades and streamlined planning pathway that the REZ legislation enables.
OX2 acquired the development rights in 2023 from Australian renewables developer ACEN Australia, which had secured the site and initial approvals. The Swedish company, which operates across onshore wind, solar, and storage in Europe and Australia, reached financial close in late 2024 and held the sod-turning ceremony in March 2025. Construction is targeting commercial operation in 2027. The project connects via the existing 330 kV Liddell-Muswellbrook line, avoiding the need for new greenfield transmission – a critical advantage given the well-documented delays plaguing the Central-West Orana REZ’s backbone infrastructure.
Coal mine rehabilitation meets grid pragmatism
Siting a utility-scale solar-battery hybrid on a rehabilitated open-cut coal mine is not merely symbolic; it solves three hard engineering and economic problems simultaneously. First, the land is already disturbed, cleared, and owned by a single entity (Idemitsu, the Japanese coal miner), eliminating the fragmented landholder negotiations that routinely add 12-18 months to greenfield solar developments in NSW. Second, the site sits directly adjacent to the Liddell 330 kV substation – formerly the connection point for the 2 GW Liddell power station, retired in 2023 – meaning the project plugs into high-capacity transmission that would otherwise sit underutilised. Third, the mine’s rehabilitation obligations under NSW law require progressive landform reshaping and vegetation; co-locating solar arrays on the final landform satisfies both the mining lease surrender conditions and the project’s land requirements without double-handling earthworks.
This model – repurposing mine voids, buffer land, and grid connections – is replicable across the Hunter. Glencore’s Ravensworth complex, Yancoal’s Mount Thorley Warkworth, and Whitehaven’s Narrabri underground all have adjacent 330 kV or 132 kV infrastructure and large rehabilitated or buffer landholdings. If the OX2 project demonstrates bankable economics, the Hunter could see a pipeline of 2-3 GW of similar mine-site hybrids over the next five years, effectively creating a “brownfield REZ” within the legislated zone.
Hybrid solar-storage economics in a two-hour market
The 200 MW/400 MWh battery (two hours at rated power) reflects the current sweet spot in Australia’s National Electricity Market (NEM) for storage duration. AEMO’s 2024 Integrated System Plan projects that 2-4 hour storage will provide the bulk of firming capacity through 2035, with longer-duration technologies (pumped hydro, 8+ hour batteries) only becoming cost-competitive after coal retirements accelerate post-2030. By pairing 400 MW of solar with a two-hour battery, OX2 can shift midday generation into the 5-8 pm evening peak, capture negative-price arbitrage during spring solar oversupply, and provide Frequency Control Ancillary Services (FCAS) – a revenue stack that typically contributes 15-25% of battery project income in the NEM.
The project’s capacity factor will be constrained by the solar resource (roughly 24-26% in the Upper Hunter) and the battery’s two-hour limit, yielding an annual output on the order of 850-900 GWh – equivalent to roughly 3-4% of Eraring’s current annual generation. That points to a key reality: even at 400 MW, this project replaces only a fraction of a single coal unit’s energy contribution. The Hunter REZ’s 7.5 GW target implies 15-20 projects of this scale, or a mix of larger wind and solar-hybrid developments, to fully replace the 5.5 GW of baseload coal exiting by 2028. The OX2 project is a necessary first step, but the deployment rate must average 1.5-2 GW per year through 2028 to avoid a capacity gap – a pace NSW has not yet achieved in any REZ.
European capital, Australian execution risk
OX2’s entry continues a pattern of European utilities and developers – including Neoen, Engie, RWE, and Statkraft – deploying balance-sheet capital into Australian renewables at a pace that outstrips many domestic players. OX2’s model – develop, build, sell down to institutional owners post-commissioning – aligns with Australian superannuation funds’ appetite for de-risked, operational brownfield assets. The company has approximately 1.5 GW of Australian projects in late-stage development across solar, wind, and storage, suggesting the Muswellbrook project is a platform play rather than a one-off.
However, execution risk remains high. The Hunter’s construction labour market is tight, with competing demand from the Hunter Transmission Project (the REZ’s backbone 500 kV line), Transgrid’s HumeLink, and multiple coal mine rehabilitation contracts. EPC contractors capable of delivering 400 MW solar plus 200 MW battery simultaneously are limited to a handful of tier-one firms (e.g., UGL, Downer, Decmil), and their order books are full through 2026. Any slippage in the 2027 commercial operation date would have cascading implications for the REZ’s credibility and the NSW government’s legislated emissions targets.
Who this affects
- Utility planner (Transgrid/AEMO): The project validates the Hunter REZ’s “existing infrastructure first” connection strategy, but the 2027 COD target must be treated as optimistic in reliability modelling; contingency plans for Eraring/Bayswater retirements should not assume this capacity is firm until commissioning tests are passed.
- Storage/hybrid developer: The mine-site + existing substation model is now de-risked for follow-on projects; developers with land options near Liddell, Bayswater, or Vales Point substations should accelerate approvals to capture the same transmission advantage before host capacity is fully subscribed.
- Policy analyst (NSW/DCCEEW): This project alone does not close the 2028 capacity gap; the government’s Capacity Investment Scheme tenders must deliver 1.5+ GW/year in the Hunter specifically, not just statewide, to maintain reliability margins as coal exits.
- Institutional investor (super funds, infrastructure funds): A European developer building to sell down at COD creates a near-term pipeline of brownfield, contracted hybrid assets – exactly the profile Australian super funds have mandated allocation targets for; expect competitive bidding for the Muswellbrook asset once operational.
What to watch next
- Hunter Transmission Project final investment decision (late 2025): The 500 kV backbone line unlocks the REZ’s full 7.5 GW; delay beyond 2028 would strand projects like Muswellbrook on constrained 330 kV lines.
- OX2’s next Australian financial close (likely late 2025): The company’s 1.5 GW pipeline includes wind hybrids in the New England REZ; a second close would confirm the platform strategy and deepen the European capital pool in Australian renewables.
- Eraring retirement confirmation (Origin board decision, 2025): If Eraring extends beyond 2025, the Hunter REZ’s urgency diminishes; if it firms 2025, the 2027 Muswellbrook COD becomes a critical reliability milestone.
- Battery duration creep in NEM tenders: If AEMO’s 2026 ISP shifts optimal storage duration to 4+ hours, the Muswellbrook battery’s two-hour design may face early economic obsolescence; watch for OX2 or future owners to stage a duration upgrade.
Bottom line
The Muswellbrook solar-battery project is the Hunter REZ’s proof-of-concept: it demonstrates that mine-site rehabilitation, existing transmission, and European development capital can combine to deliver hybrid renewables faster than greenfield alternatives. But at 400 MW solar and two-hour storage, it covers only a sliver of the 5.5 GW coal exit by 2028. The REZ’s credibility – and NSW’s reliability – now hinges on whether the next 10-15 projects can reach financial close in 2025-2026 and whether the 500 kV backbone proceeds on schedule. Without that acceleration, the Hunter REZ risks becoming a symbolic gesture rather than a functional replacement for the coal fleet it was designed to succeed.
Read the full report at RenewEconomy
Original source: RenewEconomy (Australian clean energy news)
Note: facts and figures attributed above to RenewEconomy (Australian clean energy news) reflect that outlet's original reporting. Broader context, cross-sector connections, and forward-looking scenarios reflect independent analysis by our editorial team.
About this article: Drafted by Energy Ai with AI-assisted research and writing based on public reporting, then reviewed under our editorial process before publication.
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