Householders who have applied for the Water Conservation Grant could see the €100 in their bank accounts today.
The Department of Social Protection has just started paying out the grant to more than 156,000 people who opted to get the money via electronic transfer.
More than a quarter of a million applications have been made for the grant so far.
Everyone who registered with Irish Water is eligible for the €100 payment, regardless of whether they have paid their bill or not.
Applications can be made up until the October 8.