A quarter of houses in high flood-risk areas are attracting extra insurance premiums of hundreds or even thousands of dollars, new Treasury data shows.
And across New Zealand, insurance premiums have increased by nearly 30 percent in just 18 months, with more insurers now pricing down to address level as their risk modelling becomes more sophisticated.
Experts have previously warned that insurance will become prohibitively expensive or impossible to get at all for some properties as the risk from climate change-driven weather events continues to rise.
Actuarial consultancy Finity has monitored insurance premiums on behalf of Treasury since late 2022, for a dataset of properties chosen to match New Zealand's natural hazards profile.
Since October 2023, the monitoring has expanded to include 1710 properties in suburbs around the country that are known to be flood-affected, either by river or surface flooding.
The most recent report, based on April 2024 data but released this week, showed that insurance remained widely available.
The exception was Canterbury, where nearly half of properties could not get more than a single quote.
For high flood risk properties, 92 percent could also get online quotes from at least two underwriters - but 25 percent of those were quoted an additional flood premium of at least $250.
In the most extreme cases, the flood premium was up to $4500, although the vast majority of elevated flood premiums were less than $1000.
Despite broad availability, properties in some flood-affected suburbs did struggle to get multiple online quotes.
In the Christchurch suburbs of Avondale and Woolston, no high-risk properties in the dataset were able to get more than one online quote. Even low-risk properties struggled, with just 10 percent of Woolston properties and no Avondale properties able to secure a second quote.
"We can see by the difference in availability between high/low risk properties and no risk properties that at least some insurers are likely using flood risk as a driver for underwriting criteria," the report authors said.
Suburbs that had high seismic risk as well as high flooding risk had the lowest availability, the report said.
Overall premiums have also increased by sometimes thousands of dollars since monitoring first began in September 2022, prior to Cyclone Gabrielle.
Nationally, the average cheapest online quote for the properties in April was $1839, an annual increase of 15 percent, and up 29 percent since monitoring began.
Climate change researchers have warned that insurers could start to withdraw from some communities at high risk from extreme weather events by the end of the next decade.
Research published in 2020 by the Climate Sigma group, looking at just the main centres, projected that 10,000 coastal homes would face full insurance retreat - where insurance is either not available at all or becomes prohibitively expensive - by 2050.
The Insurance Council, major insurers, and councils have all urged successive governments to come up with a national climate adaptation plan that will spell out how to protect or even move those communities out of harm's way.
Parliament's finance and expenditure committee is currently hearing submissions as part of a cross-party inquiry into climate adaptation.
It will report back in September and its recommendations will be used to help develop legislation to be introduced in early 2025.
