A spokeswoman for the Minister for the Environment has rejected a claim that one-third of households are not suitable for the installation of water meters.
Executive manager with Dublin City Council Tom Leahy is quoted by the Irish Times as saying that one third of homes will always be on a standing charge and will never have water meters installed.
This would amount to around 533,000 households - based on an estimate of 1.6 million households in the State.
Mr Leahy said that apartments would pose particular problems - as would houses built between the 1940s and 1960s.
A spokeswoman for Minister Phil Hogan said that, according to the Department's figures, a maximum of 300,000 households are likely to be without water meters after the initial stage of the metering process.
She said the quickest and easiest homes would receive meters first, and the figure of 300,000 would come down as the metering process continued.
The exact number of homes to receive water meters in the initial stages would be a matter for Irish Water, she added.