"Many still assume they only pay an annual administration fee of $20-$30 because management fees (which are often higher) are not disclosed in a manner that people can understand."
Stubbs has calculated that Kiwis have already paid more than $40 million in fees in January alone and will likely pay more than $525m this year.
More than 2.7 million people belong to KiwiSaver with more than $45 billion invested in the scheme.
"KiwiSaver fees are the largest household expense people have never heard of.
"Over their lifetime, an average KiwiSaver member will pay $54,700 in fees, way more than they will spend on power or their mobile phones," he said.
But Blair Vernon, managing director of KiwiSaver provider AMP Financial Services, said fees were only one of a number of things people should consider when choosing a KiwiSaver provider or fund to invest in.
"Some low-fee offers for example offer only basic member services so it's a more 'do-it-yourself' approach to retirement saving, and we know that doesn't work for many people based on our experience of advising them for decades."
Vernon said people needed to focus on whether they had a coherent and realistic plan for their retirement and what they wanted to achieve.
"KiwiSaver is just one part of that - and a singular focus on fees absent of the much needed advice and support that many need is missing the bigger challenge for New Zealanders."