At the end of August, more than two million New Zealanders were signed up, with more than $12 billion now invested nationwide.
National media reports suggest some pensioners add water to milk to make it last longer and stay in bed to save on heating costs.
Mr Duffill said even if someone was moved into a rest home, to get their own bathroom would cost an extra $70 at today's prices.
"I just don't know how people are surviving, especially those old ladies who may not have someone around the house to do maintenance.
"Even getting a plumber in ... costs a couple of hundred dollars," he said.
Retirement Commissioner Diana Crossan said people needed to realise how small the superannuation allowance was.
"People who work should understand that unless they put savings aside themselves they could end up living off New Zealand super alone and that's really tough.
"It means fish and chips are a treat - and if you don't want life where fish and chips are a treat then you should start doing something early."
KiwiSaver was an easy and convenient way for employees to save for the later years, Ms Crossan said.
Individual workers have saved more than $5 billion since the scheme's 2007 introduction.
Government contributions total $4.88 billion and employers' contributions total more than $2.7 billion.
Ms Crossan said planning for retirement was about weighing up current options with future pay-offs, such as those associated with the KiwiSaver scheme.
"There are times in your life when you have to make these decisions about how you manage your money differently.
"It might be worth going into debt to get an education, because your education will give you a better income in the future," she said.
"It might be also worth going into debt to buy a house and get a mortgage ... because owning your own home is part of your retirement savings."
About 8 per cent of New Zealanders aged over-65 lived in hardship, and many of them were renting their homes, she added.
Other figures showed about 250,000 people had opted out of KiwiSaver since it was introduced.
More than 80,000 people had taken contribution holidays at the beginning of September.
A contribution holiday can be taken by someone who has been in the KiwiSaver scheme for 12 months and wants to take a break from saving.
The numbers
Hawke's Bay savers: 71,365 participants
Total savers nationwide: 2,002,840 participants
65-plus withdrawals: Just over 5000
Number of people on a contribution holiday: 86,468 as at September 5
- Source: Inland Revenue
