The Reserve Bank says lending restrictions it brought in this month should lower house price growth by between one and four percentage points in the next year.
From 1 October, banks must keep mortgages to people with low deposits to no more than 10% of their total mortgage lending.
The Reserve Bank says the restrictions are likely to reduce the growth in housing credit by between one and three percentage points.
The central bank says it modelled what might happen in a severe housing market downturn when interest rates were rising sharply and calculates that these lending restrictions imposed for two years would reduce bank losses by 10% - 15%.
The bank says it will be difficult to fully assess the impact of the restrictions because it can't know what would have happened without the restrictions.
It says it will be reporting regularly on its assessment of the impact the restrictions are having.