The economy may have shrunk by more than three percent during the level four lockdown, according to a Reserve Bank research paper.
The bank has looked at the potential impacts on the economny during various levels and estimates the four week lockdown cost the economy about $10 billion in lost production.
It said a similar length of time under alert level 3 would cost the economy around $5b.
The paper said the amount of lost production roughly halved as restrictions eased through to alert level 1.
The effect is not uniform across the economy but some sectors, such as tourism, will take the hardest hit.
The Reserve Bank said it was using the estimates as part of its information flow for next week's monetary statement, which analysts will see further action to support the economy.