Hartmann also has a weekly personal finance column for the Herald Online with tips on getting financially savvy.
"When you are choosing which fund to be in, after finding funds with the right level of risk for you, fees are the next most important thing to consider," Hartmann says. "But it's not a matter of simply finding and picking the cheapest fund out there.
"Imagine if you parked your savings in a conservative fund for 33 years just because it had the lowest fees: your results would typically be tens of thousands less than if you chose a growth fund over such a long period.
"So first figure out the right type of fund for you, then compare fees.
"Sorted's KiwiSaver fund finder lets you do just that."
With KiwiSaver and managed funds in general, you don't necessarily get what you pay for.
"Higher fees don't necessarily mean higher returns or better service.
"Studies show that the opposite is often the case - funds with higher fees tend to result in poorer performance because of the way they siphon off any gains they might make.
"... the goal is to keep the costs down and the performance up.
"The KiwiSaver fund finder displays performance data on dozens of funds after fees have been charged [and taxes too]. Based on newly available KiwiSaver data each quarter, it lets you compare apples with apples. So you can more easily gauge what's reasonable for you and immediately see which funds' fees are above or below average for a given type of fund.
"KiwiSaver fees come in two forms: a flat, fixed annual membership fee [these range from to $60 a year, on average $34] and a percentage fee, which is a percentage of your account balance.
"Percentage fees tend to be higher in riskier funds.
"When you start out in KiwiSaver and your balance is still low, the flat fees have a big effect. But over time, when you, for example, have $100,000 in your account, the percentage fees will have a bigger effect overall, especially if you are saving over a long period.
"So the amount of fees you pay can make a big difference to your results by the time you retire.
"You can see the long-term effects of fees on your KiwiSaver with Sorted's KiwiSaver fees calculator, which gives you an estimate of how much you are likely to pay up to age 65. This is another way to see how fees compare in similar types of funds."
But again, you want to be comparing funds of the same type.
"When fund managers invest your savings and buy and sell shares and other assets, they manage in either an 'active' or a 'passive' way.
"Active managers usually trade shares frequently, looking to enhance their returns, while passive managers simply buy and hold a range of shares - often the shares in a market index such as the NZX 50.
"Active management costs more, so the fees tend to be higher. The KiwiSaver fees calculator shows which funds are active and which are passive.
"The short of it all is that when choosing a fund, you need to decide whether the fees you are paying are worth it.
"At Sorted we recommend selecting a fund with the right level of risk for you, with reasonable fees, with services and communications from the provider that you want, and which hasn't performed consistently poorly compared with similar types of funds," Hartmann says. "There are many other criteria you could use in choosing a fund, but these are the factors that are most important, in that order."
Disclaimer: Information provided is stated accurately to the best of the respondent's knowledge at the time of publication. It is general in nature and should not be construed, or relied on, as a recommendation to invest in a particular financial product or class of financial product. Readers should seek independent financial advice specific to their situation before making an investment decision.
To have your KiwiSaver questions answered by the NZ Herald's panel of industry players email Helen Twose, helentwose@gmail.com. Sorry, but Helen cannot answer all questions, correspond directly with readers, or give financial advice.
