The head of the Snowy 2.0 project told a Senate estimates committee that the expense of terminating the development had not been modelled despite a recent reassessment of construction costs.
Snowy Hydro chief executive Dennis Barnes also revealed replacing the project with batteries had been modelled at a cost of $80 billion.
The evidence comes days after the company announced the hydro-electric scheme would cost between $22.2 billion and $25 billion to complete, up from $12 billion in 2023.
Mr Barnes, who appeared before the committee for more than two hours, said "just under $12 billion" had already been invested in the pumped hydro project designed to store up to 350 gigawatt hours of renewable energy.
But the project was such a vital piece of Australia's renewable energy transition that the cost of abandoning it had not been considered, he said.
"We have done the analysis of what would we do if we were to change contractor," Mr Barnes said.
"But we have not done the analysis on what it would cost to terminate the project given the importance of the project to the grid."
The company did calculate how much Snowy 2.0 would cost to replace with eight-hour batteries capable of delivering 42,000MW, he said, and came to a figure of $80 billion.
The project would require significant government funding to reach completion in 2029, Mr Barnes said, although he did not specify how much additional money would be asked of taxpayers.
"I do believe that the contingency and risk buffer we've applied to the balance ... is an appropriate buffer and can be completed for that," he said.
"The complexity of this project means that there are no cast-iron guarantees, though."
More than half of the project's current funding came from temporary and shareholder loans.
Innovation Minister Tim Ayres, who appeared before the committee on behalf of Energy Minister Chris Bowen, criticised previous coalition ministers for failing to identify cost shortfalls in the project.
While he did not commit further funding to the scheme, Mr Ayres said it would be a vital piece of energy infrastructure that would help to keep electricity prices down.
"The costs of abandoning it are immense for the Australian community," he said.
"We will see it through and we will get it done and we are relying upon Snowy Hydro to do that work."
