Central-West Orana REZ: NSW’s first REZ, status check

Drive the Golden Highway out past Dunedoo on a clear morning and you’ll see the survey pegs before you see any steel. I did this run on the bike back in winter, out from Merotherie towards Wellington, and what struck me wasn’t the wind farms already spinning off in the paddocks. It was how much of the transmission corridor is still just cleared easement and access tracks, more than three years after this zone became the first renewable energy zone declared in NSW.

Central-West Orana REZ, or CWO as everyone in the industry now shorthand it, covers a rough triangle of the state’s central west running from Dubbo down through Wellington, Dunedoo and out towards Merriwa. It was declared under the NSW Electricity Infrastructure Roadmap back in 2021, and it was always going to be the test case. If NSW couldn’t get its first REZ built on time and on budget, the other five zones in the pipeline had a real problem.

Where the build actually sits right now #

The core piece of infrastructure is a new high-voltage transmission backbone, roughly 500kV double-circuit running the length of the zone, designed to gather up wind and solar generation scattered across dozens of properties and get it to the existing grid near Wellington and on to Sydney. Construction is underway along sections of the corridor, with easement acquisition, substation works and tower footings progressing at different paces depending on landholder negotiations. It is not finished. Energisation has slipped from the original public timeline, and EnergyCo NSW, the state body coordinating REZ delivery, has been upfront in project updates that the schedule has moved.

That matters because a chunk of the generation this zone is meant to host is either built or close to it, sitting there waiting for firm network access. Curtailment in the interim isn’t a hypothetical; it’s the default condition for a generator connected ahead of its transmission.

Capacity, access and the MW/MWh distinction that keeps getting blurred #

Let’s be careful with the numbers here, because REZ coverage gets reported loosely. The declared hosting capacity for Central-West Orana sits in the vicinity of 4.5 gigawatts of generation capacity, per EnergyCo’s own project material. That’s the theoretical ceiling the network is being built to carry, not what’s currently contracted or built. Access rights allocated to generators through EnergyCo’s access scheme add up to a smaller, firmer number, and firm access is the thing developers actually need before a bank will finance a wind or solar farm.

Here’s a rough worked example to keep the units straight. A 400 MW solar farm running at a capacity factor around 25 to 28 percent, reasonable for this part of inland NSW, produces somewhere near 900 to 1,000 gigawatt-hours a year. A 400 MW wind project in the same zone, with capacity factors more often sitting in the mid-30s to low-40s percent range, produces meaningfully more energy off the same nameplate figure. Two projects can carry an identical MW rating on a spreadsheet and still deliver very different annual MWh. If you want the fuller version of that argument, our piece on what firming means and why gas keeps coming up walks through why that gap is the whole reason firming exists as a category.

Who’s actually building the wires #

This is the part that makes Central-West Orana genuinely different from a standard Transgrid augmentation. EnergyCo NSW ran a competitive process and landed on ACEREZ – a consortium bringing together Acciona, Cobra and Endeavour Energy – as the network operator responsible for financing, building, owning and operating the transmission backbone under a long-term contract, rather than the usual regulated-utility model where a business like Transgrid recovers costs through the AER’s revenue determination process.

It’s a privately financed, competitively tendered REZ network, a structure NSW pitched as faster and cheaper than the conventional regulated build. I’ll give the model credit for trying something different: the regulated investment test process has genuinely slow features. But a private consortium financing model shifts a chunk of project risk onto financing conditions and contractual milestones rather than a regulator’s cost-of-capital determination, and when interest rates and construction costs move against you, that risk shows up as delay and price variation rather than a formal regulatory reset. That’s roughly what’s happened here.

The cost story, and why I’d treat any single figure with suspicion #

Cost estimates for the CWO transmission project have moved substantially from the numbers first floated publicly, and by the state’s own account the figure now sits well past $2 billion, more than double early public estimates. I won’t hand you a precise current number, because it’s the kind of figure that shifts with each contract variation and financial close update, and reporting it as fixed would be misleading. What’s consistent across EnergyCo’s own updates is the direction: costs have gone up, not down, driven by a mix of construction cost inflation, landholder easement negotiations running longer than scheduled, and the sheer complexity of threading a new high-voltage corridor through agricultural land held by hundreds of separate owners.

That last point is worth sitting with. This isn’t a green-fields transmission line through crown land. It’s negotiated easement, farm by farm, along roads like the Golden Highway and side tracks off it, and every one of those negotiations has its own timeline. Our broader piece on Renewable Energy Zones: the plan behind the pushback goes into why that community friction was always going to be the rate-limiting step for REZ delivery generally, not just here.

ACEN’s bet inside the zone #

Among the generators with skin in this particular game is ACEN Australia, the Philippines-backed developer that’s built a genuine NSW portfolio through projects like Stubbo Solar Farm and the Valeria Solar development, both sitting inside the Central-West Orana footprint. We’ve covered ACEN’s broader NSW strategy separately in ACEN Australia: the Philippines-backed builder behind New England Solar, and the pattern there holds here too: a developer that’s committed capital on the promise of network access that’s still catching up to the generation queue.

For a solar or wind developer sitting inside CWO right now, the calculus is straightforward and uncomfortable. You’ve either built and are curtailing against a network that isn’t finished, or you’re holding off financial close waiting for a firmer transmission timeline, which means holding off construction, which means missing the window when the state actually needs the capacity.

Why it matters more than one zone’s numbers suggest #

NSW’s coal fleet is closing on a schedule that assumes replacement generation turns up roughly on time. Eraring’s exit has already been pushed once, a story we’ve tracked in Eraring power station: how 2025 became 2027, and Mount Piper and Vales Point are on their own countdowns. AEMO’s Integrated System Plan leans heavily on REZs like this one to deliver the replacement megawatts and the megawatt-hours that go with them. If Central-West Orana’s backbone keeps slipping, the state’s options narrow to either more gas peaking capacity or leaning harder on interconnectors, both of which come with their own cost and timing questions we’ve covered in NSW’s energy transition: the coal exit meets a REZ rollout running late.

It also sets the template – good or bad – for how NSW runs its remaining REZs. If the private network-operator model here ends up costing more and taking longer than the standard regulated approach would have, that’s a genuinely useful data point for New England, the Illawarra and the other zones still working through their own delivery contracts. Worth reading against our explainer on transmission versus distribution: who owns the poles and wires, since CWO is arguably testing a third ownership model altogether.

What I’ll be watching next #

The honest position is that nobody outside EnergyCo and ACEREZ has a fully current picture of the completion date, and any date I gave you today would likely be stale within a quarter. What I do watch is the pace of easement sign-offs reported in EnergyCo’s own quarterly updates, and whether curtailment figures for the generators already connected inside the zone start improving or stay flat. That’s the tell. Everything else is timeline noise until the wires are actually energised end to end.

For more on how AEMO sequences dispatch and where REZ generation slots into that five-minute market, see the AEMO website at aemo.com.au, and EnergyCo NSW’s own project pages at energyco.nsw.gov.au carry the most current public timeline, for whatever that’s currently worth.

– Anjali Rao, Grid & Storage Correspondent

Photo by Jonathan Hanna on Unsplash