Planning the transition points: Keeping the SWIS secure as renewables scale
I also acknowledge the Whadjuk Nyoongar people, traditional owners of the land and the first to harness its energy. Their beliefs and practices endure and shape our state today, and I pay my respects to Elders past and present.
The most challenging moments in an energy transition aren’t necessarily the ones that jump to mind, like the closure of a coal plant or a prolonged period of minimum system demand.
It's when yesterday's operating model no longer works for today's power system.
It's when the rules, tools and procedures we've always relied on have to be adapted — fast — to the power system that is emerging.
And if we only recognise that moment when it arrives, we've recognised it too late.
Because by then, the technology may not be proven, the right market arrangements may not exist, the workforce may not be trained and the operating procedures may not be developed, tried or tested.
That understanding sits at the heart of how AEMO thinks about and plans for the energy transition.
Not as a straight line from one power system to another, but as a series of moments where the system changes in important ways and preparation is paramount.
We were reminded of that lesson on the other side of the world about a year and a half ago.
As the people of Spain and Portugal sat down for lunch on Monday the 28th of April last year, voltage instability spread through the network, generators disconnected and the situation escalated faster than operators could arrest it.
The power system collapsed and the lights went out for 50 million people.
The outage wasn't caused by a shortage of generation.
In simple terms, the system failed because critical system services to keep the power system secure weren't there when they were needed.
I want to be clear that Western Australia is not Spain and the South West Interconnected System (SWIS) is certainly not the European grid.
AEMO has studied the outage closely, and it has reinforced for us the fundamental importance of ensuring that the technical capabilities needed to keep a changing power system secure are understood, available and operational before they are required.
For the rapidly-changing SWIS, achieving that readiness is a shared responsibility.
The WA Government leads the state's energy transition, Western Power plans the future network and AEMO provides the operational, engineering and market insights to help keep the system secure and reliable.
Together, we face two connected challenges:
- ensuring there is enough generation and storage to meet demand as the economy grows and generation retires, and
- replacing the essential system services those generators have traditionally provided.
The Government’s Power System Security and Reliability Standards Review is essential to achieving this goal.
It is focused on establishing an integrated framework for the changing system, including coordinated planning arrangements, a system-strength framework and updated technical standards for grid-forming and grid-following technologies.
AEMO is working closely with the WA government on this initiative.
Our own work on transition planning complements the review and will feed into it over time.
Transition planning is designed to facilitate a system-wide view, allowing AEMO to look across the system and identify when today’s operating arrangements need to evolve, so that we can work effectively with Government, Western Power and industry on the capabilities needed before those points arrive.
That’s why identifying the critical transition points in the SWIS is one of the most important jobs AEMO is doing in partnership with government and industry today.
Because the SWIS is different.
WA is not the Iberian Peninsula and we're not the east coast of Australia.
The physics are the same, and the learning travels.
But the solutions must be right for the SWIS.
AEMO’s role is to support the introduction and integration of the right solutions at the right time, with transparency and practical insights drawn from our position at the heart of the power system.
Our approach is grounded in practical experience, from managing reliability today through the Reserve Capacity Mechanism to planning for the decade ahead through forecasting and the SWIS Engineering Roadmap.
It draws on Western Power’s Transmission Plans and AEMO’s work with Energy Policy WA (EPWA) on several planning and modelling processes.
This work can also inform longer-term whole-of-system planning, including the government’s Future Energy System Outlook, or FESO as it’s called.
Today, I want to share how AEMO is thinking about transition points, and how we are working with government and industry to put essential system services in place in the SWIS at the right time, efficiently and affordably.
The transition is often described as a road from today’s system to a future system. But it’s not a straight road and I think most people in this room would agree it’s definitely not a smooth road.
This slide shows the fundamental change we are managing.
On the left is the power system we inherited, built primarily around large synchronous generators.
On the right is the system emerging around renewable generation, storage and inverter-based technology, supported by gas.
Along the way are points where system conditions change enough to require a different operating response, and the most important date is not the date of the event, it’s the date when preparation begins.
In technical terms, Transition Points are key events or milestones that impact electricity reliability and security and require a material change in how AEMO manages the power system security.
Material changes are those that can no longer be managed effectively through existing operating procedures, normal market arrangements and policy.
These are changes that require something new or changed, for example:
- new capabilities in AEMO or transmission network control rooms,
- deployment of new technologies,
- new coordinated reforms across the sector, or
- changes to the Electricity System and Market Rules.
We start preparing well in advance of the transition point – because transition planning works backwards.
If a synchronous generator retires in 2029, and replacing one of its current capabilities requires something new or different, then 2029 is already too late.
Our planning works backwards: What needs to be built? What needs to be procured? What needs to change in our control rooms? And when does each decision need to be made?
Because a transition point might be years away, but the decision point may be today.
AEMO’s approach to transition planning in the west draws on leading national and international experience, including the east coast’s Transition Plan for System Security, Ireland's DS3 program, and Great Britain's System Operability Framework and Stability Pathfinder.
They each adhere to a common principle of modelling the changing system, identifying the point at which existing arrangements may no longer be enough, then working backwards from that point.
And the reason these approaches look similar is because we are all facing a similar challenge.
Around the world, we’re moving from power systems built around big thermal machines to systems with much more renewable generation, storage and inverter-based technology — supported, in Australia’s case, by gas.
And compared to many systems, our transition is faster and more ambitious.
Ten years ago, almost 90% of electricity in the SWIS came from coal and gas.
Over the past year, renewable resources supplied more than 40% of energy, peaking above 90% at times.
Consumers are driving the transition with their investment decisions just as much as industry and government.
The SWIS has fundamentally changed, and there’s no going back.
As the system decarbonises and generation technology shifts from synchronous generation to inverter-based resources, reliability assessments have to change as well.
The power system operating envelope is being stretched by the fact that renewable resources don’t carry with them the innate system security benefits provided as a by-product of the spinning machine generators in coal and gas power stations.
Inverter-based resources, including batteries, can provide many of those capabilities, but they do so differently and must be designed and integrated accordingly.
While transition planning has proven itself globally as a structured, sound and effective approach, its implementation is inherently local.
It is built on a rigorous, evidence-based screening process which includes reviewing potential Transition Points based on key Power System Security and Reliability criteria such as Frequency Stability, Oscillatory Stability and Resource Adequacy.
It involves assessing the risk trajectory of the SWIS, collaborating with industry and government on potential solutions, then delivering the strategic initiatives to prepare for system change.
This is AEMO’s current view of the key Transition Points facing the SWIS.
Next year is critical with the planned retirement of Collie Power Station, an event AEMO has been preparing for over many years.
After that, the next transition point comes when major network projects such as the Clean Energy Link North come online at the start of 2028.
The next transition point is already underway in the cumulative decisions of thousands of West Australian consumers to install rooftop solar panels and household batteries.
From 2029, AEMO has forecast there will be 200 megawatts of Virtual Power Plants, which has been reflected in a commensurate reduction in the ‘Reserve Capacity Target’ for that year.
For AEMO, these dates are deadlines for readiness that ensure we have the most effective interventions to hand to respond to the most significant risks.
It involves prioritisation, so we examine what we can do with our existing tools, while accurately forecasting shortfalls and assessing possible solutions.
Risk identification is a crucial element of the process.
The 2026 WEM Electricity Statement of Opportunities — the WEM ESOO — is not a transition plan.
Its purpose is to assess whether WA will have enough of the right capacity to meet demand reliably over the next decade.
But its findings provide important signals about how the SWIS is changing, and where transition planning needs to focus.
WA has sufficient capacity forecast to meet reliability requirements over the next three years.
But the amount, and critically, the type of capacity the SWIS needs is changing.
The Peak Reserve Capacity Target is forecast to grow from around 5.7 gigawatts today to almost 7.5 gigawatts in the middle of the next decade.
Rooftop solar is continuing to reduce daytime operational demand, while batteries and Virtual Power Plants are increasingly able to absorb, store and shift energy.
Capacity is no longer the only question that matters because duration, flexibility, ramping capability and state of charge are growing in significance.
AEMO's role is to focus on the initiatives that will have the greatest impact on achieving that security in our rapidly changing system.
Gas will remain an important part of WA's energy system as coal power stations retire and more renewable energy comes online.
Gas also presents one of the clearest examples of why averages do not tell the whole story.
The forecasts in the WEM ESOO make it clear that as renewable energy and storage increase, gas-powered generation may operate less often, on average.
And when the system needs it, it may have to ramp faster, reach higher peaks and sustain output through longer periods of low renewable generation.
So lower annual gas use does not necessarily mean lower system dependence. In fact, the reliability value of gas can increase even as its average utilisation falls.
Planning for that role is not about slowing or reversing the transition. It is about ensuring the electricity and gas systems can support the system securely with the right infrastructure, contracts and operational coordination needed during periods of system stress.
We saw the contours of the future role of gas very clearly from the AEMO control room on Monday the 25th August 2025, when Perth experienced its coldest day in 50 years.
Demand rose sharply as temperatures dropped, then fell just as quickly when the sun returned.
Rooftop solar generation was highly variable, and some battery systems discharged earlier than expected, leaving less stored energy available for the evening peak.
Adding to the complexity, a few thermal units were constrained by wet coal and gas supply was tight.
The most important fact is that customers were not affected.
But the day was a sobering glimpse into a future SWIS: more weather-dependent supply, sharper ramps, greater interaction between distributed and grid-scale resources, and periods when gas demand can rise very quickly.
It was a powerful example of the complexity our teams now manage in real time, across weather, technology and market behaviour — often within hours.
It was also clear that no single technology solves the challenges of keeping the system secure through this kind of combination of circumstances.
It requires visibility, forecasting, flexible capacity, sufficient stored energy, secure fuel supply, essential system services and clear coordination across the sector.
Looking ahead, there may be moments when demand for gas is higher than the available or contracted supply.
AEMO is working closely with the Department of Energy and Economic Diversification to identify practical, cost-effective solutions that support both the electricity and gas systems.
So, what is AEMO doing now to help ensure transition readiness?
First, AEMO is continuing to strengthen and evolve its modelling, forecasting and operational capability, and working with government and Western Power to align our understanding of emerging risks and identify clear technical requirements and planning signals.
Second, industry needs visibility and lead time to develop the right solutions. Depending on the capability required, that may involve generation, storage, grid-forming technology, synchronous compensation, demand flexibility, network investment, gas arrangements or new system services.
Third, these insights need to connect into coordinated, whole-of-system planning, which is exactly what the Future Energy System Outlook — the FESO — is designed to achieve, with its focus on detailed scenario-based study to guide planning and infrastructure investment in the SWIS to 2050.
The SWIS is already showing us the shape of the next stage of the transition.
Non-battery demand is falling, evening ramps are growing, and consumers are becoming increasingly active participants.
Batteries are changing how the system behaves and coal generation is retiring.
The role of gas is steadily shifting from one of an everyday source of energy towards having a more targeted but still critical role in reliability.
None of those changes is unexpected.
But each changes what the system needs and when it needs it.
That is the purpose of transition-point planning: to see the moments coming when the system will need something different, and to make the decisions, investments and reforms early enough.
Keeping the SWIS secure through this transition will not happen by accident.
It will take purposeful choices, practical delivery and close coordination across Government, Western Power, AEMO and industry.
By doing this work together now, we make sure that Western Australia can meet this transition with confidence and shape the system we need for tomorrow.
Thank you.