Christchurch Age Concern says it is dealing with an increasing number of elderly people struggling to stay warm in their homes over winter.
Christchurch Age Concern chief executive Simon Templeton said his staff used to encounter older people who could not afford to heat their homes properly only occasionally, but now they were 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 were bad for people's health, as it decreased their strength, balance and mobility.
Mr Templeton said people were also breathing in freezing air, which could lead to respiratory problems.
Meanwhile, almost a third of the requests for help to the Christchurch Mayor's Welfare Fund in the past year were from people struggling with their power bills.
Figures from the Christchurch City Council showed that, in 2014/15, the fund paid just under $110,000 to 300 applicants to help with their power bills.
A total of 960 applicants were paid $377,000 in emergency assistance in the same period.
The council said the fund had already had 19 applications since 1 July, with people seeking almost $9000 in grants for help with power bills.