250 megawatts of generating capacity, six to eight hours of storage, sitting inside two worked-out gold pits a couple of hours west of Cairns. That’s the headline spec for Kidston pumped hydro, and it’s been the headline spec for long enough now that I’ve started timing my check-ins on the project against other things: the last time I rang around for an update, Snowy 2.0’s tunnel boring machine was still called Florence and still stuck. Kidston has had its own version of stuck, just quieter and less photogenic.
The site itself is genuinely striking. The old Kidston gold mine, north-west of Mount Surprise in the Etheridge Shire, has two enormous open pits left over from decades of mining that ended in the early 2000s. Genex Power’s idea, which goes back to a feasibility study last decade, was to turn those pits into the upper and lower reservoirs of a pumped hydro scheme – pump water uphill when power is cheap or abundant (think the middle of a sunny north Queensland day), let it run back down through turbines when the grid needs it. It’s not a new idea in engineering terms. What’s unusual is building it inside a hole someone already dug for you, which saves a huge amount of civil works compared with greenfield pumped hydro.
Where the project actually sits right now #
Let’s be careful with the terminology here, because “commissioning” gets used loosely in trade press and it covers a lot of ground. Genex’s own ASX filings describe the Kidston Pumped Storage Hydro project (KPSH) as having completed major civil and mechanical works, with the water conveyance tunnel, powerhouse and electrical infrastructure substantially built, and the project moving through staged testing of the pump-turbine units toward full commercial operation. That’s a very different status to “under construction” and a very different status to “generating at nameplate capacity into the market every day.” Readers should treat anything described as “commissioning” as meaning the hardware exists and is being proven, not that it’s earning full revenue yet.
The broader Kidston Clean Energy Hub, which Genex has built out around the original pumped hydro concept, now includes a 50MW solar farm and a 150MW wind farm already operating and feeding the pumped hydro’s daytime pumping load, plus the 250MW/2GWh pumped storage asset itself. The logic is tidy on paper: solar and wind generate cheap daytime energy on site, some of which pumps water uphill, and the pumped hydro discharges into the evening peak. It’s one of the few projects in the NEM where the firming asset and at least part of its charging source sit behind the same fence.
What it actually costs, and who’s paying #
The capital cost of KPSH has moved over the life of the project, as these things do – cost escalation in pumped hydro construction has been a theme across the NEM, not a Kidston-specific problem, and I’d point anyone wanting the Queensland comparison toward our earlier look at Borumba pumped hydro and where Queensland’s 2GW bet actually stands. Kidston’s funding stack has included debt backed by the Clean Energy Finance Corporation and support through Queensland and federal mechanisms, alongside Genex’s own equity and, more recently, capital from its majority shareholder J-Power, the Japanese utility that took effective control of Genex in 2024. We’ve covered that ownership shift in more detail in Genex Power under J-Power: what the Kidston bet looks like now, and it’s worth reading alongside this piece because the financing story and the construction story are not the same story, even though they get conflated constantly.
J-Power’s involvement matters for a reason beyond the balance sheet. Japanese utilities have decades of pumped hydro operating experience that the Australian market, frankly, doesn’t have much of outside Tumut and Wivenhoe. Whether that experience translates cleanly to commissioning a scheme inside former mine pits with their own peculiar geotechnical quirks is still being tested, literally, as the turbines go through their staged trials.
Why this is harder than a spec sheet suggests #
I’ll say the obvious thing plainly: pumped hydro commissioning is not like switching on a battery. A grid-scale battery energy storage system is modular. You energise strings, you run software validation, you’re largely done in weeks. A pumped hydro scheme has rotating mechanical plant, enormous volumes of moving water, and a tunnel system that has to prove itself under real hydraulic load before anyone will sign off on full commercial operation. Reversible pump-turbines in particular have a reputation in the industry for throwing up vibration and cavitation issues during early running that take real time to diagnose and fix. None of that implies anything has gone wrong at Kidston specifically, I haven’t seen anything in Genex’s filings suggesting a fault, it’s just the nature of the technology, and it’s one reason commissioning timelines for pumped hydro worldwide tend to blow out relative to the original schedule, Snowy 2.0 being the extreme local example.
The distinction between power and energy matters enormously here too. 250MW is what Kidston can push into the grid at any instant, at full output. 2GWh is how long it can sustain that before the upper reservoir runs dry and needs re-pumping. Those are very different numbers doing very different jobs, and when AEMO’s capacity assessments talk about Kidston’s contribution to reliability, it’s the energy figure – the duration – that tends to matter more for evening peak coverage than the megawatt figure alone. Readers who want the general version of this trade-off should look at our explainer on pumped hydro versus batteries and what actually firms the grid, because Kidston is a decent real-world test case for exactly that comparison: long-duration storage that complements, rather than competes directly with, the four-hour batteries now proliferating across the NEM.
What AEMO’s planning actually assumes #
AEMO’s Integrated System Plan treats pumped hydro broadly, and Kidston specifically, as part of the deep storage the grid will need as coal retires through the 2030s. The ISP doesn’t bank on any single project; it models a portfolio, and Kidston sits in that portfolio as a committed or near-committed asset for the Queensland region, distinct from the much larger Borumba scheme Queensland’s state-owned Powerlink and CleanCo are pursuing further south, and distinct again from Snowy 2.0 in New South Wales. If you want the full planning document, AEMO publishes the ISP and its supporting Queensland-specific appendices on its website, and it’s genuinely worth reading the regional sections rather than just the executive summary: the regional detail is where projects like Kidston actually get their numbers.
Queensland’s own state energy planning, which we’ve written about in Queensland’s energy plan rests on two pillars and one cliff face, leans heavily on pumped hydro as the long-duration backbone behind an enormous build of wind and solar. Kidston is smaller than Borumba and smaller again than anything Snowy-scale, but it has one advantage those bigger projects don’t: it’s much closer to being finished. A 250MW asset that actually commissions this year or next does more for grid reliability in the near term than a 2GW asset that’s still years from first concrete.
The transmission question nobody asks loudly enough #
Here’s my mildly contrarian read on Kidston, and it’s not really about the plant itself. The pumped hydro and the wind and solar around it sit in far north Queensland, a long way from the major load centres in the state’s south-east. Powerlink’s transmission build in that part of the grid, including the work tied to the broader North Queensland Clean Energy Hub concept, has to keep pace for Kidston’s output to actually reach customers efficiently rather than being constrained off during high-output periods. We’ve looked at Powerlink’s bigger regional transmission ambitions in Powerlink’s big bet: CopperString and the north-west minerals grid, which is a different corridor but the same underlying problem: generation in the north, demand in the south-east, and a transmission network that has to be built roughly on schedule for any of it to matter commercially. I’d argue the generation side of north Queensland’s renewable build has consistently outpaced the public conversation about whether the wires connecting it are keeping up, and Kidston, for all its engineering interest, doesn’t change that dynamic on its own.
There’s also a market design wrinkle worth flagging. Pumped hydro earns revenue through a mix of energy arbitrage: buying cheap power to pump, selling expensive power to generate, and increasingly through capacity-style contracts or ancillary services. AEMO’s five-minute dispatch engine, which we’ve explained in detail in how the NEM actually dispatches power every five minutes, rewards an asset like Kidston precisely because it can respond fast and sustain output for hours, not just minutes. Whether Kidston’s revenue stack ends up leaning more on arbitrage or more on contracted capacity will say something about how AEMO and the Queensland government see the role of mid-sized pumped hydro in a grid that’s also getting flooded with grid-scale batteries doing a similar job over a shorter duration.
What commissioning success actually looks like #
For a project like this, “done” isn’t a single date, it’s a sequence. Synchronisation to the grid, proving each pump-turbine unit across its operating range, demonstrating sustained full-load generation and pumping cycles, and then AEMO accepting the plant into normal dispatch without special conditions attached. Genex’s own disclosures to the ASX are the right place to track that sequence, rather than press release language about “milestones,” which can mean almost anything. I’d treat any claim of full commercial operation with the same scepticism I’d apply to any other generator’s first-year capacity factor claims – wait for a couple of quarters of dispatch data before drawing conclusions about how the asset actually performs against its nameplate numbers.
I keep coming back to the pits themselves when I think about this project, honestly. There’s something satisfying about an old gold mine, the kind of hole in the ground that usually just sits there as an environmental liability once the ore runs out, being repurposed as grid infrastructure that will probably still be running long after most of us have stopped writing about it. Whether Kidston clears its final commissioning hurdles cleanly or with the sort of hiccups that have dogged bigger pumped hydro builds elsewhere in the NEM is the only real open question left. The pits aren’t going anywhere. The turbines just need to prove they can keep up with them.
– Anjali Rao, Grid & Storage Correspondent
Photo by Fré Sonneveld on Unsplash