The $950 million gas-fired Hunter Power Project at Kurri will run on diesel fuel for up to six times longer when it opens later this year.
It was always intended for the 750 megawatt peaking plant to run on diesel until a gas lateral from Killingworth was completed, however, Snowy Hydro has applied to extend that period from 175 hours to up to 1100 hours.
A spokesman said the State Significant Development Application was designed to provide extra flexibility in the event of unforeseen gas supply delays.
"The Hunter Power Project is scheduled to begin operations in December 2024, marking the start of the testing and commissioning phase for one of its two generators, which will initially run on diesel fuel," he said.
"We will sequence the commissioning of the second unit and the introduction of gas, and expect the Hunter Power Project to be fully operational, with both generators able to operate on both fuels, in the few months following the start of testing.
"While the modification proposes to increase the operating hours on diesel to 1100 cumulative hours, this is only for the calendar year 2025 and is a worst-case scenario should any delays to gas supply occur."
But the application to extend the use of diesel has outraged groups that have opposed the plant since its inception.
"Both gas and diesel are polluting fossil fuels. But what this application shows is Snowy Hydro has plans to burn a lot more particulate heavy diesel for longer," Lock the Gate Alliance spokeswoman Fiona Lee said.
"This will have a serious and negative impact on the health of the Kurri Kurri community, which was recently ranked in the top 10 worst asthma hotspots in the country."
Lock the Gate cited the plant's original approval, which stated it would only burn diesel for two per cent of the year. The modification will increase that to up to 12.5 per cent of the year.
"This application to burn six times more diesel than first planned makes Chris Bowen's claims that the Kurri Kurri power station would someday run on green hydrogen look like little more than hot air," Ms Lee said.
"The Kurri Kurri fossil gas plant should never have been built, particularly not with hundreds of millions of public dollars. Renewable energy firmed with big batteries should have been prioritised, and should be prioritised now. Renewable energy wouldn't generate any harmful 2.5 particle pollution. It won't make asthma rates worse, and it won't contribute to dangerous climate change."
The Snowy spokesman said gas-powered electricity generation would remain critical to enabling Australia's renewable energy transition and meeting peak demand in what is a highly seasonal market.
"As more renewables come online, the fast-deployment capability of gas will be essential to ensuring power is still available to homes and businesses when wind and sunlight is not," he said.
