For drivers under 20, the limit was already zero.
Across Auckland's three police districts of Counties Manukau, Waitemata and Auckland Central, 2493 new-level offences were dished out in the first 12 months.
Canterbury was the single highest district with 989 drivers ticketed.
In total, 19,046 motorists were caught drink-driving from January-September 2015.
Information on how many were for the new lower-level limit was not available. But in 2014, there were 20,969 drink-driving offences and 24,539 in 2013.
National road policing manager Superintendent Steve Greally said he believed the new legislation was working and there was anecdotal evidence the new law had seen a reduction of about 15 per cent in offences above the 400mcg level.
"That is extremely encouraging for the long-term.
"It seems like Kiwis are doing a great job of taking drink-driving more seriously," Greally said.
"We really need a five-year window to identify trends. But I believe this legislation is one of the best we have seen for road safety."
He said police were committed to "change the culture of New Zealanders" around drinking, including drink-driving.
"There is no such thing as a standard drink, there is no safe limit. Our message is if you're going to drive, don't drink at all.
"We can charge with manslaughter for those who have knowingly driven drunk and ended up impacting people's lives. In those cases, to me, it's as unacceptable as murder," he said.
"Getting caught is secondary, what we're really talking about here is danger to life."
Over the past three years New Zealand's death toll has risen steadily, from 246 in 2013 to 312 last year.
Although alcohol is only one factor in road incidents, Greally said there should be evidence on the actual impact versus the death toll in a couple of months.
"The rising road toll is obviously a concern. Alcohol is responsible for around 26-27 per cent of crashes, while speed is around 30-32 per cent.
"We should know end of March what the alcohol trend has done since the limit was lowered."
Over the limit
251-400mcg alcohol litre of breath:
• Drivers caught under the lower drink-driving limit face a $200 infringement fee and 50 demerit points.
• If you acccumulate 100 or more demerit points from driving offences in two years, you will be suspended from driving for three months.
Over 400mcg of alcohol:
• Maximum penalty for first or second conviction three months imprisonment or up to $4500 and mandatory disqualification at least six months.
• Third or subsequent offence earns disqualification for more than a year, a fine up to $6000 or up to two years' prison.
