Australia's biggest power station is running out of coal. 

Origin Energy runs Eraring - Australia’s biggest power station - which is fed with coal from the nearby Mandalong coal mine owned by Centennial Coal.

Mandalong provides coal directly to the Eraring station on a conveyor belt, but reports say no coal is being produced at Mandalong at present, leaving Origin to source it from elsewhere.

Origin Energy - which recently announced Eraring would be closing in 2025, seven years earlier than planned - has told the Australian Stock Exchange that its coal stockpiles are running low at its Lake Macquarie plant, north of Sydney.

With nothing coming in on the conveyor belt, it says it has had to organise trains to bring new coal in, but the trains it commissioned are competing for freight line space against other coal and commuter trains.

Origin says trains to Eraring have been bumped in favour of ones travelling to the Port of Newcastle for the lucrative export market.

“It is a market-wide issue, it is not just Eraring, other power stations are affected, and it's just that Origin is saying so publicly,” the company said.

Origin typically stockpiles up to 1.6 million tonnes of coal at its Eraring power plant site, but insiders claim that pile is now very low.

Workers have been “scraping up the dregs off the bottom of what's left of the coal stockpile to keep things going”, reports allege.