The clean-up bill at Victoria's Hazelwood coal fired power station has blown out more than half a billion dollars.
French energy giant Engie - Hazelwood's majority owner - has added an extra $686 million to its original estimate for decommissioning, site remediation and mine rehabilitation, bringing the total to $743 million.
The brown coal-fired station will close its doors on March 31 this year, with years of work ahead to decommission the site, the company says.
Engie Australia's latest accounts were presented to ASIC earlier this month, and show the total includes $439 million for the mine and $304 million for the power station site and surrounding areas.
"The provision represents our best estimate of the present value of the future costs of the required work," an Engie spokesman said in a statement on Friday.
"That work will take place over multiple years and may lead to variations in future expenditure."
The company says Hazelwood is the first mine in Australia of this type and size to be rehabilitated and many "specialist external consultants" will be needed, blowing out the original cost estimates.
The state government says the clean-up will be entirely Engie's responsibility.
"It's our expectation that the full cost of rehabilitating Hazelwood will be borne by Engie, and not the state," Resources Minister Wade Noonan said in a statement.
Greens Leader Richard Di Natale said the huge cost of the closure will cost taxpayers.
"If you ever hear a coalition minister talking about how cheap coal is, always remember there is a hidden cost and it is Australian taxpayers who have to meet that cost," Mr Di Natale told reporters on Friday.
A spokesman for the Latrobe City Council said it was seeking confirmation that the costs won't fall to its ratepayers.
