Ten years after South Australia’s blackout, can batteries keep the grid secure?

Tesla and Ampyr Energy leaders reflect on how Hornsdale helped reframe the role of batteries — and the new system-security challenges emerging as Australia’s grid becomes increasingly inverter-based.Ten years after South Australia was plunged into darkness, its power system looks markedly different from the one that failed in 2016.

The statewide outage on 28 September 2016 occurred after extreme weather damaged transmission infrastructure and triggered a rapid sequence of generation losses. When South Australia separated from Victoria, the rate of change of frequency in South Australia reached about 6 hertz per second — too fast for the existing under-frequency load shedding scheme to arrest the collapse, according to the Australian Energy Market Operator (AEMO).

For Shane Bannister, Tesla’s Head of Business Development and Project Sales, Energy APAC, the event remains visceral.

“I vividly remember that blackout: standing in the middle of the Adelaide CBD in pouring rain, watching police try to manage traffic in pitch darkness after their flashlight batons had gone flat,” Bannister told Energy Insights.

“When I think about what has changed most, it is the acceptance that the traditional path to system security and reliability — large, centralised spinning machines providing inertia and system strength — is now under question.

“There have been numerous significant system events in recent times that would likely have led to widespread outages had it not been for the response and contribution of grid-forming and behind-the-meter Battery Energy Storage Systems (BESS).”

That shift is increasingly visible in the architecture of power system planning itself. AEMO now produces an annual Transition Plan for System Security, bringing together planning for inertia, system strength and other security needs and identifying points at which the way the grid is operated must be materially altered.

Alex Wonhas, Chief Executive of Ampyr Energy Australia, said the change has been fundamental.

“The biggest shift is that system security is now treated as something to be actively engineered and procured, rather than assumed as a free by-product of synchronous machines,” he told Energy Insights.

“Ten years ago, terms like system strength, inertia, ramp rates, minimum demand and sub-synchronous oscillations were specialist terms. Today they are openly discussed well beyond just technical circles.

“Just as important, the toolkit to manage these issues has vastly expanded. A planner's options used to be essentially synchronous generation, transmission lines and synchronous condensers. Now grid-forming batteries and other advanced inverter based technologies enable surgical interventions to key issues.”

From experiment to mainstream

Few assets symbolise that transition as clearly as the Hornsdale Power Reserve.

The original 100 MW/129 MWh Tesla battery entered the National Electricity Market in late 2017, less than 15 months after the blackout.

Its early impact was particularly visible in frequency control ancillary services (FCAS). In the first quarter of 2018, total NEM FCAS costs fell 57% from the previous quarter to $25 million. AEMO attributed the fall partly to new competition from Hornsdale and aggregated demand-response provider EnerNOC, which together supplied about 20% of Raise FCAS during the quarter.

During one South Australian FCAS requirement in January 2018, the participation of Hornsdale Power Reserve and Hornsdale Wind Farm helped limit prices to $248/MWh, compared with prices of about $9,000/MWh during previous periods when the local FCAS requirement applied, which AEMO estimated reduced costs by about $3.5 million over five hours.

Then-AEMO chief executive Audrey Zibelman said the experience demonstrated how new technologies could “ensure power system security and simultaneously encourage competition”.

Wonhas called Hornsdale “a genuine turning point, in Australia and arguably globally”.

It demonstrated two things at once: that batteries could do things the incumbent fleet simply could not — sub-second frequency response, riding through separation events — and that they could be built at a speed the rest of the system had never assumed was even possible, he said.

“That changed the conversation from ‘can storage work?’ to ‘how much, how fast, and where?’

“A decade later, batteries are the fastest-growing asset class in the NEM.”

Batteries become a system resource

The scale-up since then has been substantial.

The Australian Energy Regulator said installed battery capacity almost tripled during 2025 alone, rising from 2.2 GW to 6.1 GW and adding flexible supply during evening peaks.

The scale of the development pipeline dwarfs the capacity already installed. AEMO’s 2026 Integrated System Plan says battery projects progressing through the connections pipeline have increased from around 3 GW in September 2022 to 45 GW in 2026. About 70% of this proposed capacity is paired with grid-forming inverters to provide additional system services, including frequency control and a stable voltage waveform to support system strength.

The technology is also changing how the wholesale market operates. In the June quarter of 2026, total FCAS costs across the NEM fell to $9.2 million — the lowest quarterly level recorded since at least 2016, according to the AER.

Bannister said experience during system disturbances had gradually changed attitudes towards inverter-based resources.

“We have seen traditionally conservative network owners and operators begin to recognise that distributed, inverter-based technologies can and do provide the same services in a more balanced and controllable manner,” he said.

South Australia itself provides perhaps the clearest illustration. In September 2025, AEMO reduced the minimum synchronous-generator requirement under defined conditions from two generators to one. Its transition planning is now examining the requirements for periods with zero synchronous generators operating.

A different reliability challenge

Yet the growth of batteries has not eliminated reliability or security risks.

In June this year, the AER found that periods of high South Australian demand coincided with very low wind output and a “cascading reduction” in battery state of charge, contributing alongside network constraints and market behaviour to significant price outcomes.

The next challenge is also materially different from 2016.

The NEM reached a record 78.6% instantaneous renewable contribution for a half-hour on 11 October 2025, while renewable resource potential exceeded 100% of demand in 55 half-hour intervals during October. AEMO is explicitly preparing the grid to operate securely and reliably during periods of 100% instantaneous renewable penetration.

Wonhas said those periods would be the next major technical test.

“Within a decade we will routinely be near 100% for hours at a time,” he said.

“That is the real proving ground.”

For Bannister, meanwhile, the challenge now extends beyond generation and storage to the networks connecting them.

He said transmission infrastructure is not being built quickly enough to accommodate growth in both generation and demand.

A decade after the blackout, the lesson may therefore be less that Australia has solved power system security than that the tools available to manage it have fundamentally shifted.

Hornsdale helped demonstrate what batteries could do. The task for the next decade is to determine how far those capabilities can be extended as coal exits and electricity demand grows. Australia must now learn to operate an increasingly inverter-based grid without relying on the assumptions that governed the old power system.