Queensland Just Switched on 1.7 GWh of Grid Batteries. Here's What It Means for You.

This is one of those details that sounds obvious once you hear it but explains a lot about where Australia's big batteries are going.

The most expensive and time-consuming part of building a grid-scale battery is not the batteries themselves. It is the transmission connection. Getting approval to connect a 300MW anything to the high-voltage grid takes years of planning studies, environmental approvals, and tens of millions in infrastructure upgrades. Sometimes the grid connection costs more than the battery.

Coal plants already have those connections. Tarong has massive transmission lines running straight to the south-east Queensland load centres. Swanbank sits on a grid connection that was built to handle a coal-fired power station. When you plonk a battery on the same site, you inherit all of that infrastructure. No new transmission lines. No five-year approval process. You just plug in.

It is the same logic behind Stanwell's next project: a 300MW / 1,200MWh battery at Rockhampton, co-located with the Stanwell coal plant. And you will see this pattern repeat across the country as more coal stations wind down. The grid connection is the golden ticket.

Remember the warehouse analogy? Right now, Queensland's electricity market has a problem that is best described as a badly timed surplus. During the day, there is too much solar and not enough demand. In the evening, there is too much demand and not enough supply. Gas peaker plants fill that evening gap, and they charge accordingly... sometimes $10,000 to $20,000 per megawatt-hour during extreme peaks.

Grid-scale batteries sit right in the middle of this mismatch. They absorb cheap daytime solar (sometimes buying at negative wholesale prices) and sell into the evening peak. Every megawatt-hour a battery dispatches during peak is a megawatt-hour that a gas peaker does not have to generate. Over time, that compresses the evening price spikes that drive high retail electricity rates.

With 550MW of new battery capacity now live in Queensland (and 260MW more from Supernode), the state has significantly more evening flexibility than it did three months ago. That does not mean electricity bills drop overnight. Wholesale prices flow through to retail gradually, typically over 6 to 12 months as retailers adjust their hedging positions. But the direction is clear.

This is the question I get asked most often when grid battery news hits the headlines. And the honest answer is: it is complicated, but mostly no.

Grid batteries and home batteries do different jobs. Yes, there is some overlap in the “store cheap solar, use it at peak” logic. But the value of a home battery is not just arbitrage. It is self-consumption (using your own solar instead of buying from the grid at 30+ cents per kWh). It is blackout protection. It is VPP participation, where your battery earns money by responding to grid events. And it is independence from whatever retailers decide to charge you next year.

What grid batteries will do over time is reduce the severity of evening price spikes. If you are on a time-of-use tariff and your home battery is primarily earning its keep through peak/off-peak arbitrage, that margin could narrow. But self-consumption savings (the biggest value driver for most households) are barely affected. You are still avoiding the full retail rate every time you use your own stored solar instead of buying from the grid.

We covered this in more detail in our deep dive on grid batteries and home battery ROI. The short version: grid batteries shift the value mix slightly, but they do not kill the home battery business case. Not even close.

If you have heard the term “duck curve” before, this is exactly what these batteries are designed to flatten. The duck curve describes how electricity demand looks when you subtract rooftop solar generation: it dips dramatically during the day (when solar is pumping) and spikes sharply in the evening (when solar drops off and everyone turns on their appliances).

That evening ramp, going from minimal demand to full demand in the space of two hours, is what makes electricity expensive. Gas peakers fire up, spot prices surge, and retailers pass the cost on. Grid-scale batteries are essentially purpose-built to clip that evening spike. Charge during the belly of the duck, discharge during the neck.

With over 200,000 home batteries now installed across Australia as well, the combined effect of grid-scale and residential storage is starting to reshape the demand curve in real time. Home batteries do their part during the same 4pm to 9pm window, just at a smaller individual scale. It is the same warehouse logic, just distributed across hundreds of thousands of garages instead of concentrated on a single site.

Queensland is not slowing down. Stanwell's second battery at Rockhampton (300MW / 1,200MWh) is under construction and will more than double the company's storage portfolio when it comes online. Supernode Stages 2 and 3 at Brendale will push that single site past 3 GWh. The state government's investment of $514 million in battery infrastructure this financial year makes it one of the largest state-level commitments to storage anywhere in the world.

Nationally, the pipeline is staggering. AEMO's data shows around 64 GW of proposed generation and storage in the NEM, with roughly half being battery projects. Not all of those will get built, but even a fraction would fundamentally change how the Australian grid operates. We are moving from a system designed around big coal plants that run 24/7 to one where solar provides the energy and batteries provide the timing.

For anyone thinking about a home battery, this context matters. The grid is getting more battery storage every month. That means fewer blackouts, smoother pricing, and (eventually) lower retail rates. It does not mean home batteries become pointless. If anything, the shift towards time-of-use pricing and dynamic tariffs makes having your own storage more valuable, because it gives you control over when you buy from the grid and when you do not.

Coming back to the warehouse analogy: Queensland just built two enormous warehouses that will buy cheap solar during the day and sell it back to the grid every evening. That is good for everyone. Lower wholesale price spikes mean lower bills, eventually. Less gas generation means lower emissions. More grid stability means fewer blackouts.

For home solar owners, the equation has not changed as much as the headlines suggest. Your panels still generate more than you use during the day. A home battery still lets you use that surplus in the evening instead of buying from the grid at peak rates. And the federal battery rebate still knocks thousands off the upfront cost, at least while the current STC factor holds.

The coal-to-battery transition happening at sites like Tarong and Swanbank is genuinely significant. These are not pilot projects or demonstration facilities. They are $500 million industrial assets that will operate for decades. When a state-owned energy company invests that kind of money in battery storage on a coal plant site, it tells you everything about where the energy system is heading.

Whether you are thinking about a home battery, already have one, or just trying to understand your electricity bill, the grid is changing fast. And for once, the change is working in your favour.