Drive the gravel road into the old Kidston gold mine in north Queensland and you come over a rise to find two enormous water-filled pits looking at each other across about 700 metres of ridge. That gap, and the roughly 220-metre fall between the upper and lower pit, is the entire engineering premise behind Genex Power. It’s a neat trick turning an exhausted mine into a 250MW pumped hydro battery. The harder trick, the one that’s occupied Genex for the better part of a decade, has been getting paid properly for doing it.
Genex Power is no longer a company you can easily buy shares in. Japan’s J-Power, formally the Electric Power Development Co, completed its takeover of Genex through calendar 2024 and into 2025, and the stock came off the ASX. That matters more than it sounds. A pumped hydro project with a multi-decade payback profile sits far more comfortably on a strategic utility’s balance sheet than it ever did bouncing around as a small-cap ASX stock answering to quarterly sentiment. I’ve said before, writing about Kidston’s status through various stages of construction, that this was always a project better suited to patient capital than public markets. J-Power’s full ownership is that thesis playing out.
What’s actually built at Kidston #
Three assets make up the Genex portfolio now, and it’s worth being precise about what each one does because people conflate them constantly.
The Kidston Solar Project, split across KS1 (50MW) and the larger KS2 development, supplies daytime generation and, more importantly for the pumped hydro story, surplus midday power to run the pumps. The Kidston Pumped Storage Hydro project (KPSH) is the 250MW/2,000MWh asset. That’s eight hours of storage at full output, a duration no battery currently operating in the NEM gets close to. And there’s a wind component, the Kidston Wind Farm, intended to help fill the gap when solar drops off in the evening and demand for pumping still exists.
The pumped hydro plant reached a major construction milestone through 2024 and 2025, with first water fill and commissioning activity underway at the site. Readers who want the full construction chronology should go back to our dedicated piece on Kidston’s build timeline; I won’t re-litigate every delay here, except to say that re-purposing a mine void for hydraulic infrastructure always throws up surprises geotechnical engineers didn’t see in the resource model, and Kidston has had its share.
Bouldercombe: smaller, faster, already earning #
While Kidston has taken the better part of a decade from concept to commissioning, Genex’s Bouldercombe Battery Project near Rockhampton went from financial close to operation in a couple of years. It’s a 50MW/100MW battery, modest by the standards of projects like the Waratah Super Battery in New South Wales, but it’s been running and earning revenue in the NEM for a while now, providing frequency control ancillary services and arbitrage in a part of the grid – central Queensland – that badly needs more dispatchable capacity close to load.
Let’s be careful with that comparison, because duration is the whole story here. Bouldercombe gives you two hours of storage at rated power. Kidston’s pumped hydro gives you eight. Those are different products solving different problems, and conflating “battery” with “pumped hydro” because both store energy misses what each is actually good for. Bouldercombe is built for fast frequency response and short daily arbitrage cycles. Kidston is built to shift a genuinely large block of energy – two gigawatt-hours – from the solar trough to the evening peak, potentially running for multiple hours through a still, overcast stretch when batteries with shorter duration have already emptied. I wrote at length about this distinction in the piece on pumped hydro versus batteries, and Genex’s own portfolio is close to the textbook illustration of why you’d want both.
The revenue underpinnings matter as much as the concrete #
Here’s where the story gets less romantic and more about spreadsheets. Kidston’s pumped hydro secured a long-term offtake arrangement with EnergyAustralia years back, giving the project revenue certainty that a lot of standalone storage assets in the NEM simply don’t have. Separately, Queensland’s state-owned arrangements and various federal and state support mechanisms, including funding support through the Clean Energy Finance Corporation and ARENA at earlier stages, have underwritten parts of the capital stack.
That layering of contracted revenue, concessional finance, and now a strategic owner with deep pockets is precisely the combination pumped hydro needs, because the economics genuinely don’t work on spot-price exposure alone for an asset this size. The Capacity Investment Scheme, which I’ve covered in detail in how the CIS actually works, has become the default mechanism AEMO and the Commonwealth now use to de-risk exactly this kind of long-duration asset, and it’s reasonable to expect Kidston or future Genex developments to sit somewhere in that scheme’s tender rounds, even where an individual contract isn’t always publicly itemised in detail.
Why J-Power wanted it #
J-Power isn’t a speculative financial buyer. It’s one of Japan’s larger power generation companies, with decades of experience operating pumped hydro domestically, where Japan has relied on the technology for grid balancing since long before batteries were commercially relevant. Pumped hydro is a mature, well-understood technology to a company like J-Power in a way it simply isn’t to most Australian investors, who’ve had almost no local pumped hydro built since Wivenhoe went up in the 1980s, aside from the much larger and vastly more contested Snowy 2.0 project.
That’s the genuine strategic logic for J-Power taking Genex fully private: a technology its engineers know intimately, in a market, north Queensland, that AEMO’s Integrated System Plan consistently flags as needing more firm, dispatchable capacity as the state’s ageing coal fleet, including Stanwell’s and CS Energy’s units, steps down through the 2030s. For a Japanese utility looking for a foothold in a market going through the transition at speed, an operating pumped hydro asset with contracted revenue is a sensible, if unglamorous, way in.
North Queensland’s wider transmission problem #
Kidston doesn’t sit in isolation. Its value depends enormously on transmission capacity to actually move that stored energy where it’s needed, and north Queensland’s grid is thin relative to the renewable resource sitting on top of it. Powerlink has been progressively augmenting transmission in the region, and projects like CopperString further west are part of the same broader push to give north and north-west Queensland generation somewhere useful to send its output.
Genex’s own wind and solar assets at Kidston benefit from, and are somewhat constrained by, the same transmission build-out timeline. This is a recurring theme across Queensland’s Renewable Energy Zones: the generation and storage assets often get built ahead of the wires that would let them operate at full value, and Kidston has not been immune to curtailment risk in that sense, even with its own storage onsite to firm against it.
A measured read on where this sits #
I’ll be honest about my own scepticism here. Pumped hydro projects of Kidston’s scale have a well-earned reputation for blowing both budget and schedule: Snowy 2.0 is the cautionary tale everyone cites, and rightly, and Genex’s own project history, across more than one change of major shareholder and more than one slipped milestone, isn’t spotless either. But unlike Snowy 2.0, Kidston is a much smaller, geographically simpler undertaking: no multi-kilometre tunnel boring through variable rock, no Florence-the-TBM getting stuck. It’s two adjacent, already-excavated mine pits. That’s a meaningfully lower-risk civil engineering proposition, and it’s probably the single biggest reason J-Power was comfortable taking full ownership rather than staying a minority partner.
My own view, for what it’s worth, is that Genex under full J-Power ownership is now a more boring company than it was as an ASX-listed developer, and that’s a compliment. Boring, patient, utility-owned infrastructure is exactly what long-duration storage needs to actually get built and operated reliably in this country. The quarterly-results theatre that comes with being a small-cap listed stock was never well suited to an asset with an eight-hour discharge cycle and a decade-long construction runway.
What to watch from here #
The practical test now is commissioning performance: whether Kidston’s pumped hydro plant, once fully operational, actually delivers its contracted capacity reliably through its first full wet and dry seasons, and whether Bouldercombe’s operating data, which AEMO publishes through its standard market reporting, continues to show solid utilisation in Queensland’s ancillary services markets. Readers who want to track AEMO’s own data on how the plant is dispatched can follow the published generator performance information on the AEMO website directly, rather than relying on company statements alone.
I’d also keep an eye on whether J-Power uses Kidston as a template for further Australian acquisitions. A Japanese utility with pumped hydro expertise and a newly complete first project in the NEM is exactly the profile of buyer who might come back for seconds, particularly as more Renewable Energy Zone transmission gets built and more exhausted mine sites across Queensland and New South Wales start looking like Kidston did a decade ago: a hole in the ground with a view.
– Anjali Rao, Grid & Storage Correspondent
Photo by American Public Power Association on Unsplash