Age Concern is warning that older people's health is suffering because they cannot afford to properly heat their homes.
The organisation's Canterbury branch said it was increasingly encountering older people who could not afford to heat their homes, with some opting to stay in bed all day.
Chief executive of Age Concern Auckland, Kevin Lamb, said problems were also being seen in Auckland.
Mr Lamb said the cost of living in Auckland is rapidly increasing, and many older people are having to decide between paying the rent or mortgage, or heating their homes.
He said if an older person is continually cold it is bound to have a detrimental impact on their health. This would increase the numbers of elderly people admitted to hospital with serious complications.
Age Concern Canterbury chief executive Simon Templeton said his staff used to occasionally encounter older people who could not afford to properly heat their homes, but now they are coming across them every week.
Mr Templeton said some older people were opting to stay in bed all day, because they could not afford to run heaters.
He said even a few days in bed is bad for people's health, as it decreases their strength, balance and mobility.
Mr Templeton said people were also breathing in freezing air, which could lead to respiratory problems.
Almost a third of the requests for help to the Christchurch Mayor's welfare fund in the past year were from people struggling to pay their power bills.
Christchurch City Council figures show that in the 2014/ 2015 financial year the mayor's welfare fund paid $109,892 to 300 applicants to help with their power bills.
In total the fund paid out $377,055 in emergency assistance to 960 applicants.
The council says since 1 July this year, the fund has already had 19 applications, which were seeking $8886 in grants for help with power bills.
The number of requests to the fund for help with power bills has steadily increased in recent years.
In the 2013/14 year the fund paid out $80,035 to 257 applicants to help with power bills, while in 2012/13 it paid out $79,490 to 298 applicants.