For most retirees NZ Super is not enough to live on, says Claire Matthews, Massey University.

People need just over $100,000 in savings at age 65 in order to be able to afford the most basic of lifestyles in either Auckland, Wellington, or Christchurch, research from Massey University has found.

"We estimate a single person living in Auckland, Wellington or Christchurch would need savings of at least $101,774 to make up the gap between superannuation payments and a basic level of household expenditure," Claire Matthews from the Westpac Massey Fin-Ed Centre said.

NZ Super, the country's universal state pension, is too little to live on on its own for many retirees, especially those who don't own their own homes.

Matthews said the gap between income and expenditure for New Zealand retirees continued to shrink, but rising housing and household utility bills meant NZ Super payments still didn't cover the costs of living for many retirees, she said.

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Every year Massey academics update their figures on how much it costs to live "no frills" and "choices" lifestyles in retirement.

No frills is just getting by on a limited diet, with no holidays, while choices includes better food, and holidays.

Matthews said housing and household utility bills were the most significant cost for retirees.

Thanks to the rising rental costs created by a shortage of homes in our big cities and council hiking their rates, housing and household utility bills have increased far faster than the Consumer Price Index, putting pressure on retirees.

For the 12 months to June 30 2016, Statistics New Zealand calculated that housing and household utility costs jumped 3.3 per cent, against a rise in the overall Consumer Price Index of just 0.4 per cent, Matthews said.

"That increase will have had a considerable impact on retirees, especially those living alone," Matthews said.

"Housing and household utility bills make up 24.2 percent of the basket of goods used to calculate the CPI."

"However, for retirees living alone … this category actually makes up between 26.3 percent and 29.2 percent of their total expenditure, so any increase has a disproportionate effect on their cost of living."

"So while superannuation payments went up last year by more than the CPI, in line with the increase in average wages, most retirees will still need additional income, even for a very simple lifestyle."

Matthews said costs like rates and power bills were unlikely to decrease any time soon, and the growing number of retirees renting rather than owning their own homes was also likely to ensure a continuing difference between the level of superannuation and most retirees' actual expenditure.

Some of the gap is made up for retirees with accommodation supplement, and other government allowances, which may not be available, if people amass savings in KiwiSaver.

The current cash asset test is just $8100 for a single person for accommodation supplement.

The estimated KiwiSaver nest eggs needed to add to NZ Super to achieve the "no frills" retirement for a one-person household is $101,774 for people retiring in a city, and $30,199 for people retiring in a small country town.

The amount needed for a "choices" lifestyle in a city would be $360,620.

For a two-person household, it's easier going. A "choices" city lifestyle would require a combined nest egg of $486,023, or $243,011 each.

All these sums were calculated assuming the individual, or couple, would live until the age of 90, Matthews said, though everyone's life expectancy varies.

Matthews says that while it's never too late to start preparing for retirement, getting a head start on saving can really pay off.

To save the $101,774 to make up the gap between superannuation payments and a basic level of household expenditure, people had to start as soon as possible.

"If you start saving at 50, you would need to save $127 per week to achieve that by the time you turn 65. Start saving at 40, and that reduces to $72 per week."

The Massey figures are now widely used in online KiwiSaver calculators (Kiwibank and ANZ), as well as by financial advisers, to help people work out what they need to save.

HOW MUCH WILL YOU NEED?

Assuming NZ Super's purchasing power does not change between now and your retirement, how much would households need to save to get "no frills" and "choices" retirements in cities (Metro) and country towns (Provincial).

One-person households:

* No Frills – Metro $101,774

* No Frills – Provincial $30,199

* Choices – Metro $360,620

* Choices – Provincial $388,073

Two-person households:

* No Frills – Metro $0 (you don't need to save anything)

* No Frills – Provincial $78,144

* Choices – Metro $486,023

* Choices – Provincial $402,682