Victorian Energy Minister Lily D’Ambrosio admits the state government will know the total cost of its multibillion-dollar renewable energy plan only once all the contracts involved are signed over the coming years.

D’Ambrosio was grilled at length about estimates that the transition plan would cost $20 billion, or more than four times the $4.3 billion set out by the government last month. She said the $20 billion figure – first reported by The Australian Financial Review – was wrong but could not say what the cost was or what the impact on energy bills would be.