Auckland's hospitals are now expecting to care for 120 Covid-19 patients a day at the peak of the current outbreak - more than double the current number.
Some Covid modellers expect about 300 new cases a day in the city after restrictions are eased to allow shops to open next week.
So far the highest number of patients across the three main hospitals on any day was 56 - so 120 would be a big step up.
Most hospitals would need to run two Covid wards.
DHB Covid modeller Gary Jackson said they expected numbers to peak at about 120 between the hospitals before dropping again.
Hospitals would be able to cope, because higher vaccination rates meant fewer people with the virus were likely to need hospital or intensive care, he said.
But that was partly because the DHBs were not doing a lot of their usual work - and that could not last forever.
The government had shown two scenarios based on Dr Jackson's modelling at its Monday press conference announcing its plan to ease Auckland's restrictions.
The presentation had highlighted the scenario with lower case numbers, but Jackson said the hospitals were now assuming it would be the worse of the two.
Modelling how the outbreak would impact hospitals was tricky because it depended on how well the restrictions worked, and how quickly vaccination rates climbed, he said.
But it allowed hospitals to plan as much as they could for the numbers of patients they might need to care for.