The utility needs the money to make up shortfalls resulting from the suspension of water charges
Almost €300 million of taxpayers money will be needed to make up the cost of the suspended water charges.
Irish Water expects to have a €123 million cash shortfall this year alone, with the figure reaching €125 million in 2017, according to figures obtained by the Irish Independent.
Water charges were suspended for nine months from July to allow an expert commission to examine the funding model for water services.
Irish Independent environment editor Paul Melia told Newstalk Breakfast that even if billing returns in 2017, the utility will still end up with a shortfall of over €120 million.
"If charges are reintroduced, they won't be introduced until after March of next year so they're going to miss out on three months of money," he explained.
"The other reason is they believe that householders are going to be difficult to convince to pay."
The company expects to spend a large amount on PR and marketing in the event of a return of the charges.
Anti-water charge campaigner and Independent TD Paul Murphy said that Irish Water is not factoring in the amount of money saved by suspending the charges.
"They're not taking into account that the State saves €130 million a year by not having the conservation grant which is linked to the water charges," he told Newstalk Breakfast.
"The reality is water charges raised no money whatsoever last year."
Irish Water said in a statement: "Following the suspension of domestic water charges, the government has stated its support for the Irish Water capital investment programme of €5.5 billion out to 2021." It did not comment further.