How much are batteries changing the grid?

Hey Reader, welcome to The Energy's weekly data newsletter. This week we explore the impact of booming batteries on the duck curve.

Duck swoon

Two energy executives with front row seats at the roll out of the Albanese government’s wildly oversubscribed home batteries scheme made some startling claims at the All Energy conference a couple of weeks ago.

Ryan Wavish, general manager innovation at Engie Retail, and Kirsty Gowans, head of electricity at the federal Department of Climate Change, Energy, Environment and Water both suggested the record-busting uptake was already making its mark precisely where we want it — on the belly of the 'duck curve'.

The duck curve describes the plunge in grid demand between the morning and evening peaks due to solar power flooding into the 4.2 million-plus homes and businesses that have rooftop solar panels.

It is matched by a swoon in grid prices, which can plunge from multi-$100s per megawatt hour before the sun gets going (or $1000s/MWh if things are really tight) to as low as minus $1000 a megawatt hour when solar power floods the grid.

The phenomenon makes life tough for energy users, retailers and the Australian Energy Market Operator, which must keep things in balance. A swelling pipeline of big grid-scale batteries — AEMO counts about 24 gigawatts in its latest grid Connections Scorecard — is one well-rehearsed commercial response.

Subsidising home batteries is another response, one which recognises that small scale energy infrastructure aimed at households and small businesses can — and is — being rolled out almost instantaneously compared with the glacial pace of large clean energy projects (even though grid-scale batteries are a lot quicker to get environmental and financial approvals for than utility-scale wind and solar farms).

From a virtual standing start on 1 July, the home batteries program has registered well over 2 gigawatt hours of small-scale batteries (though they won’t all be connected because a backlog has developed) in just over four months.

In South Australia at least, the belly of the duck curve appears to have shifted an hour later in two years. *Source: Engie*

Wavish said there is so much storage going in that the market is already shifting. “We're already seeing the belly of the duck move to later in the day,” he told All Energy. “We see shifts in some of those trough prices, and it will shift markets.”

We asked both Wavish and Gowans for some empirical evidence of the shifts they had described. Wavish provided the chart above, which tracks the timing of peak negative price intervals and suggests the peak negative pricing interval has moved roughly an hour later over the past two years as more storage has come online.

This chart is confined to South Australia, where Engie has been conducting an Australian Renewable Energy Agency-funded Market Active Solar trial of a product that pays solar households to curtail their solar exports when negative prices peak.

This chart doesn’t differentiate between the impact of grid-scale and small-scale batteries. But they fulfil a similar role — soaking up surplus solar and wind energy when it’s cheap and abundant, and exporting it when it’s expensive and scarce — albeit with some differences in approach.

Gowans told the same panel that she didn’t think the rate of virtual power plant participation for batteries installed under the scheme was too bad (AEMO had complained not enough battery households are participating in VPPs to maximise their benefits).

“So 25% participation is actually quite a lot, and we're already seeing those system benefits coming through in the data, in a lot of the different work that's been done now,” Gowans said. “So we can see energy system benefits already.”

However DCCEEW was unable to provide the data, because it is not yet public.

Demand and prices

The October operational demand profile over three years hasn't changed materially. *Source: Dylan McConnell, UNSW*

The next charts — furnished by UNSW Senior Research Associate Dylan McConnell — suggest it’s too early to conclude that batteries have materially moved the duck curve, even though that’s what we intuitively expect to happen.

The charts above show firstly, the absolute 'operational demand' profile for October over three years, for the five states of the National Electricity Market; and secondly normalised operational demand (accounting for year-to-year changes in underlying demand).

Operational demand is what AEMO 'sees' and what the grid has to deliver to meet the demand that’s left after 4.2 million homes and small firms self-consume their rooftop solar generation.

The charts below show volume weighted price profiles for NSW and Victoria — the largest NEM states — for October (prices above $300/MWh have been stripped out to better reflect energy value).

In these larger data charts it is not possible to discern compelling, material changes in either the timing of the trough of the duck curve, or the overall shape of our duck.

Absolute demand is up a bit through the duck curve, as we might expect. But if anything, as McConnell points out, the trough in both demand and prices has snuck forward just a little bit.

Volume weighted prices do not show material changes in the timing of the trough; prices were little changed in NSW but higher in Victoria. *Source: Dylan McConnell, UNSW*

Slim like a duck

But AEMO’s latest Quarterly Energy Dynamics provides some confirmation of the intuitive thesis. And there are some signs that suggest batteries are having the positive impact on the grid that Wavish and Gowans described.

Batteries are ramping up during the morning and — most notably — evening peaks. As a result, gas, hydro and brown coal are being called upon less in those peak demand intervals.

In Western Australia’s South West Interconnected System, for example, batteries are charging and discharging at the desired times, and prices are moderating — with lower average peak prices and a big enough drop in negative price intervals to lift the midday average price above zero — compared to the September quarter last year.

Batteries are flattening the duck curve in prices in WA's SWIS, and trimming price spreads in the east coast NEM. *Source: AEMO, Quarterly Energy Dynamics, Oct 2025*

That looks consistent with a flattening of the duck curve. AEMO doesn’t provide an equivalent chart for the NEM, but other charts point the same way, showing quarterly average discharge rates quadrupling in two years and average price spreads falling to their equal lowest in two years.

As you’d expect from this, the negative price curve shows a pronounced drop in the magnitude of negative prices in the NEM, although negative prices are still common.

We can infer from these statistical titbits that batteries are doing the job of flattening the duck curve, pushing the price trough back later in the day and reducing the extent of negative prices.

What we can’t do is quantify the separate contributions of small batteries and grid scale batteries.

Neither can we discount the effects of AGL Energy and Origin Energy’s expenditure on technology that ramps their coal plants up and down more quickly, which means black coal plants (but not Victoria’s brown coal plants) are also helping to slim the duck.

Still, DCCEEW’s Gowans isn’t in any doubt about batteries' constructive role. “I think we might see what a transformative role batteries can really play, and not just at the household level, but also utility scale as well,” she told All Energy.

“We could see some really significant change in the energy system — those batteries a bit like magic potion in some ways, for a lot of our issues.”