How Australia’s Biggest Battery Is Rewiring Coal Country

Australia just committed to turning its largest coal plant into a giant clean energy battery – 3,160MWh of storage sitting on a site that used to symbolise fossil power.

That single decision at Eraring in New South Wales says more about the future of energy than a dozen policy papers. Coal is being kept on life support for a few more years, but the replacement is already being built in parallel – and it runs on electrons, software, and smart green technology.

This matters because any serious path to net zero needs two things at once:

• Massive renewable build-out, and
• Massive energy storage to keep the grid stable when the sun and wind fluctuate.

Eraring’s transition, led by Origin Energy with Wärtsilä as the battery supplier, is one of the clearest real-world examples of how that shift actually works.

In this post, I’ll break down what’s happening at Eraring, why the 3,160MWh BESS is a big deal for Australia’s National Electricity Market (NEM), and how AI-driven controls turn a pile of lithium cells into green infrastructure that can replace coal.

From 3GW of coal to multi-GWh of batteries

The key fact: Origin is expanding the Eraring battery energy storage system (BESS) to 3,160MWh, making it Australia’s largest approved battery by energy capacity.

Eraring today is a 2,880MW coal-fired power station – the largest single-site coal plant in the country. Origin originally brought its retirement date forward from 2032 to 2025 because cleaner, cheaper generation (solar, wind, and batteries) has been undercutting coal in the NEM.

But when the Australian Energy Market Operator (AEMO) flagged potential capacity shortfalls, the New South Wales government granted Eraring a temporary life extension to August 2027. That didn’t stop the transition plan – it actually sharpened it.

Here’s how the Eraring BESS rollout has evolved:

• Stage 1: 460MW / 920MWh – construction started in 2023
• Stage 2: 240MW / 1,030MWh – approved in 2024, with grid-forming inverters
• Stage 3: +700MWh – doubling the site’s duration from 2 to 4 hours
• Stage 4: New Wärtsilä contract brings the total to 3,160MWh

On paper, that turns Eraring from a coal plant into a long-duration, multi-gigawatt-hour battery hub that can:

• Shift renewable energy from midday solar peaks into the evening demand spike
• Provide fast-response capacity during outages or transmission issues
• Deliver grid support services like frequency and voltage control

It’s not a like-for-like swap – you don’t replace coal megawatts one-for-one with battery megawatts – but the combination of storage plus renewables is already making coal structurally uncompetitive.

Why big batteries are becoming “new baseload”

The reality: large-scale batteries are now core grid assets, not side projects.

In the NEM, you’re seeing a clear pattern:

• Coal plants are either closing or being forced into fewer operating hours
• Solar and wind are flooding the market during certain hours, crushing prices
• Batteries are stepping in to stabilise frequency, support voltage, and arbitrage price swings

Eraring isn’t alone. Other big projects are reinforcing the trend:

• Waratah Super Battery – 850MW / 1,680MWh in NSW, designed as a “shock absorber” for the transmission network
• Melbourne Renewable Energy Hub – 600MW / 1.6GWh already in commercial operation in Victoria
• Proposed Gladstone Energy Hub BESS – 780MW / 6,240MWh in Queensland, paired with gas turbines

Eraring still stands out for one reason: it’s happening on the exact footprint of a coal plant, and it’s structured as part of a deliberate retirement plan.

For businesses watching this space – utilities, industrials, data centre operators – the signal is clear:

"Baseload" in a high-renewables grid looks less like a single giant smokestack and more like a coordinated fleet of batteries, flexible generation, and smart demand.

If your strategy still assumes coal-like assets will carry your risk for the next 20 years, you’re already behind.

The quiet star here: grid-forming, AI-driven control

A battery alone is just hardware. What turns Eraring into green infrastructure is software and control, and that’s where Wärtsilä’s role is more interesting than the headline suggests.

Origin has now appointed Wärtsilä for all four stages of the Eraring battery project, using:

• Quantum series BESS hardware for large-scale storage, and
• The GEMS Digital Energy Platform for energy management and real-time control.

What does grid-forming actually mean?

Several stages of Eraring – and other projects like Mortlake in Victoria – use grid-forming inverters. That’s a shift from traditional grid-following batteries that simply feed into an already stable grid.

Grid-forming batteries can:

• Set voltage and frequency references
• Provide synthetic inertia (stabilising the grid the way spinning mass used to)
• Ride through faults instead of tripping offline

In a high-renewables grid, that’s not optional. Once coal and gas retire, you don’t have a lot of physical spinning turbines left to keep the system stable. Grid-forming batteries and advanced inverters become the new backbone.

Where AI and energy storage meet

Here’s the thing about multi-GWh batteries: you don’t get value from size alone. You get value from how intelligently you operate them.

Platforms like Wärtsilä’s GEMS – and similar EMS systems across the market – typically:

• Forecast demand, prices, and renewable output using machine learning
• Optimise when to charge/discharge to maximise revenue and support the grid
• Co-optimise multiple services (energy arbitrage, FCAS, capacity, system strength)
• Monitor asset health to extend battery life and reduce degradation

That’s green technology in practice: AI turning variable renewables and storage into dependable, dispatchable capacity.

If you’re planning or procuring storage, the questions you should be asking aren’t just about megawatts and megawatt-hours. They’re about:

• What control platform runs the system?
• How does it integrate with market data and grid constraints?
• Can it provide grid-forming capabilities and system strength, or just energy arbitrage?

Most companies get this wrong by obsessing over the hardware vendor list and underinvesting in controls, analytics, and software integration.

What Eraring signals for investors and large energy users

For anyone making medium- to long-term energy decisions – investors, corporates with net zero targets, or operators of energy-intensive sites – Eraring is a useful roadmap.

1. Coal retirement is now a managed, not theoretical, risk

Eraring’s original early retirement decision, the temporary extension to 2027, and the parallel build-out of a 3,160MWh BESS show a few things:

• Policy risk is real, but it’s not random – governments are bending over backwards to keep the lights on while coal exits
• The transition solution is explicit: renewables + storage, not “clean coal” or vague offsets
• The market operator (AEMO) is actively signalling when and where capacity or system strength is short

If you’re running a portfolio or a large facility, you can plan around that. The worst strategy is waiting for certainty while competitors lock in cheaper, cleaner supply.

2. Four-hour duration is fast becoming the new standard

The Eraring battery moving from roughly two hours to four hours of duration is not cosmetic. It reflects a broader shift:

• 1–2 hour systems are great for frequency control and short-term balancing
• 4+ hour systems meaningfully shift solar into the evening peak and can support evening demand without fossil generation

We’re also seeing 6–8 hour projects proposed (like the 6,240MWh Gladstone concept). As long-duration energy storage scales, it will start to compete directly with peakers and mid-merit gas.

If you’re designing your own storage or hybrid project, ask bluntly: are you building something that only does frequency control, or something that can substitute for fossil flexibility?

3. Green technology is now an infrastructure asset class

Wärtsilä now has about 5.8GWh of BESS projects in Australia delivered, in construction or under contract. That’s not experimental – that’s a pipeline.

The broader pattern across the Green Technology space:

• Storage assets are financed, contracted, and regulated more like traditional infrastructure
• Sophisticated EMS and AI controls are treated as core IP, not afterthoughts
• Grid-forming capability is rapidly shifting from “nice to have” to “must have” in tenders

For developers and corporates, the opportunity is to treat green technology – storage, smart grids, demand response, on-site renewables – as strategic infrastructure, not as CSR or branding.

How businesses can act on this trend now

This isn’t just a story about big utilities. Eraring’s transition has direct implications for how you plan energy, resilience, and sustainability over the next decade.

If you’re a large energy user (industrial, commercial, data centre)

You should be:

• Revisiting your load profile – when do you actually consume vs when is renewable supply abundant?
• Identifying whether co-located storage or participating in a virtual power plant (VPP) could cut your energy and network charges
• Incorporating price volatility and coal exit scenarios into your procurement strategy

I’ve seen organisations save 20–30% on energy costs by pairing flexible demand with behind-the-meter batteries and smart controls, even before adding onsite solar.

If you’re an investor or developer

You should be:

• Targeting 4+ hour storage or hybrid projects (solar + storage, wind + storage) that can bid into multiple value streams
• Prioritising projects with grid-forming inverters and strong EMS platforms – these will age better as the grid decarbonises
• Stress-testing your models against faster coal/gas closures and higher renewable penetration than the conservative forecasts assume

The strongest projects over the next decade won’t just store energy. They’ll actively support system strength and grid stability – and get paid for it.

If you’re shaping a corporate net zero roadmap

You should be looking at:

• Power purchase agreements (PPAs) that bundle renewables plus storage, not just standalone solar or wind
• On-site microgrids with smart controls that can island during outages
• Partnerships with green technology providers who bring software and analytics, not just hardware

There’s a better way to approach decarbonisation than buying offsets and hoping. Eraring shows that integrating storage into your energy strategy is how you start replacing fossil risk with controllable, digital, green assets.

Where this fits in the Green Technology story

Eraring’s 3,160MWh battery project isn’t a one-off headline. It’s part of a broader pattern we’ve been tracking in this Green Technology series: AI, advanced controls, and storage turning variable renewables into reliable infrastructure.

The next three to five years in Australia will be decisive. Multiple gigawatt-hours of grid-forming BESS are moving from PowerPoint to construction. Coal plants are negotiating their exits. AEMO’s project lists are filling up with battery projects that didn’t exist five years ago.

If you’re responsible for energy strategy, this isn’t something to watch from the sidelines. It’s a template you can apply:

• Replace exposure to coal and gas with contracts backed by renewables + storage
• Use AI-driven EMS platforms to optimise how and when you use or store electricity
• Treat batteries and smart controls as core green technology infrastructure, not optional extras

Eraring shows where the grid is heading. The only real question is whether your organisation’s plans are heading in the same direction.