Big battery and CIS contract-winner seeks federal green tick for construction

A big, four-hour battery proposed for construction at the junction of three 500 kilovolt (kV) power lines in the New South Wales Southern Tablelands has lodged a referral for federal environmental assessment. 

Swallow Tail is a 375 megawatt (MW), 1,500 MW hour (MWh) battery at the connection of the Humelink, Bannaby and Southern Sydney Ring transmission lines, according to the EPBC referral. 

And yet it will still need 1.5km of new 330 kV underground lines to link it to the Bannaby substation at the heart of the electric arteries feeding NSW’s industrial centres. 

Construction is pencilled in to start in October, the referral says.  

It is one of two projects that developer Ampyr successfully won two contracts for in the third Capacity Investment Scheme (CIS) tender last year.

Ampyr, led by the former AEMO executive Alex Wonhas, is asking whether the project must be controlled under the EPBC Act.

Surveys cited in the EPBC referral did not find any threatened flora, but people on site did see a flock of 20 diamond firetails in the spring of 2025, and a pair of Gang-gang cockatoos near a hollow in the 56 hectare development footprint a few months later during the summer.

Parts of the site are covered by Goulburn tableland box-gum grassy forest, an ecological community the EPBC considers important. 

Ampyr is promising to leave the extensively farmed land better than when it arrives. 

“The project area would be progressively rehabilitated throughout construction. When construction is completed, temporary plant and equipment will be removed, and disturbed areas will be revegetated and rehabilitated,” the referral says.

“The location has also been proposed to avoid environmental impacts as far as possible.”

It says the full 144 hectare site has been designed to give a creek a 40 metre berth and avoid the Goulburn tableland box-gum grassy forest.

Big neighbours

The Swallow Tail site abuts that of the enormous 1.2 gigawatt (GW), 4.8 gigawatt hour (GWh) Hanworth battery, which if built today would be the largest in Australia.

Octopus Australia bought that battery in February as part of a “ring of batteries” it wants to build around Sydney to satisfy contracts for firm power. It’s due to start being built in June 2028.

And to the west is the 233 MW and 2576 MWh Bannaby battery, which was also a winner of the most recent NSW battery tender.

All three projects lodged state development applications at the end of 2024. 

The fourth big battery in the area is the 400 MW, 1600 MWh Big Hill battery which is yet to enter any formal approval processes and is part of Ace Power’s book.