0.3% of homes used an eighth of total water supply
Just over 2,000 of the 771,348 metered homes are responsible for using nearly an eighth of the country's total municipal water supply.
New figures from the CSO show that the average home, with a water meter, used 383 litres of water per day.
But they also show that nearly a third of the country's entire water usage is down to 3.4% of homes, which use 5,000 litres a day - over 13 times the average.
At the most extreme end, 12% of the water supply is taken up by only just over 0.3% of homes that have a meter fitted.
The figures also suggest that very few homes would be liable for charges under the new regime proposed by an Oireachtas committee.
According to the CSO, Cavan had the lowest annual average consumption at 313 litres, compared with Kerry and Tipperary which had the highest at 430 litres.
In the capital, the Dublin 2 area had the lowest average daily consumption in 2015 - compared to Dublin 6 which had the highest.
