30 Oct 2024

Australia’s clean‑energy transition chalked up another landmark in the spring quarter of 2024. The Australian Energy Market Operator’s freshly released Quarterly Energy Dynamics Q3 2024 report documents a pair of historic moments on 9 September: at 12 : 05 pm the National Electricity Market (NEM) drew 72.2 percent of its power from renewable sources, and only fifteen minutes later rooftop solar systems alone covered 38.1 percent of all instantaneous demand. Those figures are more than record‑breaking curiosities; they crystallise just how rapidly household rooftops, utility solar farms and strong September winds are reshaping the physics, economics and politics of Australia’s largest electricity grid.

The following analysis explores what drove the numbers, how various states responded, what the quarter’s price signals mean for fossil fuel generators, and why the next leg of the transition will rely as much on flexible demand and storage as it does on more photovoltaic panels.

A rare alignment of sunshine, wind and new capacity

September is typically the shoulder month that bridges the gentler sunlight of winter and the scorching intensity of summer, yet the Bureau of Meteorology recorded solar irradiation across southern Australia six percent above the ten‑year average. Those brighter skies coincided with the windiest September since 2016, giving wind farms in western Victoria and southern New South Wales a prolonged boost. The timing was fortuitous: three large‑scale solar farms—Darlington Point Stage 2 in New South Wales, Wondoan South in Queensland and Kiamal Stage II in Victoria—had all reached commercial operations during July and August, adding nearly 600 megawatts of new nameplate capacity just in time to capitalise on the weather.

Meanwhile, the long‑delayed Western Victoria transmission upgrade finally cleared its last constraint, allowing a backlog of curtailed wind and solar generation to flow unimpeded toward Melbourne load centres. Without that added transfer capacity, the headline 72 percent figure would have been physically impossible: turbines in Horsham and Warracknabeal would again have been ordered to spill excess energy to protect network stability.

Rooftop solar becomes a true power station

Five years ago distributed PV was treated by grid planners as a helpful sidekick to the heavy lifting undertaken by utility renewables. By the third quarter of 2024 that pecking order flipped. In total there are now just over 25 gigawatts of small‑scale rooftop solar linked to the NEM—double the combined capacity of the country’s remaining coal fleet— and September produced the clearest proof yet that suburban rooflines function as a single giant power plant.

Why did rooftop PV surge so dramatically? First, the economics have never been stronger. Module prices crashed a further twelve percent over the past year, and state rebate programs in Victoria and New South Wales continue to underwrite installation costs. Second, one in three new systems now ships with a battery, allowing households to absorb excess midday production rather than dumping it onto the grid when prices turn negative. Third, the revised inverter standard AS/NZS 4777.2‑2024 took full effect in August; it gives distribution‑network operators a scalpel rather than a sledgehammer when voltage rise or frequency deviations loom. Instead of ordering blanket shutdowns, networks can now instruct individual inverters to dial export limits back in gentle increments, letting many more rooftops stay online through record peaks.

How each state fared during the record event

South Australia grabbed the headlines first by recording seven separate periods of 100 percent renewable supply during the quarter. A pair of synchronous condensers near Port Augusta, together with Hornsdale’s grid‑forming battery mode, delivered the fault‑level strength that previously could come only from gas peakers. That technical underpinning allowed the state to flirt with fully renewable operation for hours at a time.

Victoria took second place, eclipsing 90 percent renewable penetration for the first time at lunch‑time on 9 September. The Kiamal Stage II solar farm and a record 3.8 gigawatts of rooftop exports pushed the state’s coal generation to its knees. Mid‑day wholesale prices in Victoria averaged minus two dollars per megawatt‑hour on four of the five sunny Sundays in September, rewarding households that had shifted pool pumps and EV charging into daylight hours.

New South Wales, while not as green at the peak, still smashed through the 70 percent ceiling twice despite Snowy 2.0 being limited to commissioning tests. Analysts believe the pumped‑hydro giant will ultimately provide enough inertia and load swing to allow NSW to match Victoria’s high‑renewable feats once it reaches full output.

Queensland exhibited the greatest rooftop surge—2.4 gigawatts of household PV at its noon pinnacle—but continued to rely on coal for roughly half of its evening demand. The Sunshine State’s Energy and Jobs Plan calls for eleven gigawatts of new firming storage by 2035 to close that gap.

Price signals: a tale of two markets

Negative pricing has become ordinary in South Australia and Victoria between 10 am and 2 pm, but the evening ramp remains brutal. Across the NEM, spot prices between six and eight pm averaged a punishing two‑hundred‑and‑forty‑eight dollars per megawatt‑hour during the quarter. Batteries, demand‑response aggregators and flexible industrial loads caught some of that spread, yet AEMO cautioned that evening volatility will persist until at least four gigawatts of additional firming capacity reach commercial operation.

Those spikes are gold for gas peakers, which—while running fewer hours overall—scored record cap‑price events. Coal stations endured the opposite fortune: their inflexible baseload output was forced ever lower during daylight, and lucrative evening margins were diluted by batteries that can charge at minus‑price midday and discharge at peak. Forward‑price curves for 2025 baseload power have already fallen twelve percent since July, eroding the viability prognosis for coal units scheduled to retire late in the decade.

Managing grid security without fossil inertia

One of the most striking lessons from September’s record day is how quietly the grid handled it. Voltage and frequency remained within normal bounds despite the unprecedented influx of variable, non‑synchronous generation. That outcome reflects three distinct advances: first, grid‑forming inverters—both at scale in batteries and on thousands of rooftops—now supply synthetic inertia and fast frequency response previously delivered by spinning coal turbines. Second, synchronous condensers in South Australia and Tasmania shore up system strength without burning fuel. Third, the six‑second fast‑frequency‑response market introduced in October allowed batteries to underbid slower, more expensive coal and hydro units in keeping frequency deviations in check. Ancillary‑service costs dropped thirty‑five percent quarter‑on‑quarter as a consequence.

What needs to happen next

AEMO’s latest Integrated System Plan suggests the NEM could sustain more than eighty percent instantaneous renewables by 2026, but that milestone depends on three moving pieces landing on time. The first is transmission: projects such as VNI West, HumeLink and Marinus Link must navigate planning appeals and begin construction promptly to move surplus solar and wind energy to where it’s needed. The second is storage: at least fifteen gigawatts of long‑duration capacity—pumped hydro, flow batteries, compressed air or otherwise—will be required to tame the ever‑steeper duck curve. The third is flexible demand. New federal smart‑charger standards, slated for mid‑2025, will require EV chargers above seven kilowatts to be remotely controllable, turning Australia’s growing fleet of electric cars into a midday sponge and overnight wind companion.

Policymakers are also expanding the Capacity Investment Scheme, with an additional four‑and‑a‑half gigawatts of firmed renewables slated for auction in early 2025. If those tenders proceed on schedule and community resistance to new transmission can be eased through more generous benefit‑sharing, the eighty‑percent mark is within sight.

The human dimension

For households, the quarter’s data confirm that installing or enlarging rooftop solar still delivers healthy returns, particularly when paired with a battery and flexible‑export capability. Retailers are rushing to roll out daytime “solar sponge” tariffs that pay customers to run dishwashers, hot‑water heaters and pool pumps when wholesale prices go negative. Small businesses with cold storage or refrigeration loads can already save thousands by adjusting operations to these new price dynamics.

For regional communities, renewables boom towns are beginning to replace shuttered coal economies. The hub around Horsham in Victoria now hosts more than one gigawatt of wind and solar jobs, while Wandoan in Queensland transitioned from a fly‑in‑fly‑out gas hub to a solar‑plus‑battery construction hotspot. Yet social licence remains fragile; locals still resist new overhead transmission lines even as they embrace local renewables investment. Bridging that gap will demand clearer benefit‑sharing, faster planning decisions and—perhaps most critically—a consistent national narrative that explains why poles and wires are the unavoidable backbone of a clean‑energy future.

Conclusion: the path to an eighty‑percent grid

Spring 2024 may come to be viewed as the quarter that turned the theoretical into the inevitable. Seventy‑two percent renewable supply—and nearly forty percent from household rooftops alone—was not a fleeting technical curiosity; it was the logical consequence of falling solar costs, smarter inverters, targeted transmission upgrades and a market finally rewarding flexibility over brute, fuel‑burning capacity.

The lesson for the next two years is clear. To make eighty‑percent renewables the everyday reality rather than a lunchtime record, Australia must keep pulling three levers at once: build the lines that move power from windy ridges and sunny plains to cities; install storage that shifts surplus sunshine into the evening; and orchestrate millions of rooftop systems, chargers and appliances so they work in concert rather than conflict.

Do that, and the NEM won’t merely manage another step change—it will render coal’s twilight not just possible but preferable, ensuring cleaner air, cheaper wholesale prices and a power system resilient enough to thrive long after fossil generators power down for good.