The average KiwiSaver balance might be slightly more than $33,000, but that hides significant variation within the scheme - and between providers.

Data from actuaries MJW released this month shows that in the year to the end of March, Consilium-owned KiwiWrap had the highest average member balance at $173,300.

The scheme only has about 400 members.

It was followed by MAS, at an average $86,200. Craigs was next at $82,900 and Milford $75,900.

At the other end of the scale, Superlife, Aurora, Amanah Ethical, BNZ and BCF had some of the lowest averages.

BCF KiwiSaver Scheme is open to members the Plymouth Brethren Christian Church and Amanah Ethical invests in line with Sharia principles.

KiwiWrap also had the highest proportion of members contributing, followed by the NZ Defence Force scheme and Kernel.

ANZ, Booster, One Answer, Fisher Plan and Fisher Funds schemes had much smaller proportions of members contributing.

Kernel founder Dean Anderson said the difference in average balance was often due to whether a scheme was a default provider or not.

Default providers have members who have landed with them without making an active choice about which provider they want to be with.

"You find the big banks, originally default schemes, are very reflect of the 'average', as they have a diversified profile that reflects the broad diversify of members. Providers where someone has made an active decision to switch to, such as Kernel, tend to have much higher average balances as it is made up of members who have been engaged, looked at the market, and are being proactive with their KiwiSaver."

The Financial Markets Authority said it was not unusual or concerning.

"The variations could be driven by a number of factors for example, the membership profile, product offering, targeted demographics, default members that make up the total membership, marketing strategies, provider tenure."

KiwiWrap is a scheme that allows investors to customise their investments.

Advisers and investors can put money into 400 investment options and the scheme focuses on providing advice.

Consilium head of advice Ben Brinkerhoff said people wanted advice when they had larger balances in KiwiSaver.

"We are the solution that allows advisers to give advice. Why do you want advice? You think to yourself I can't mess this up… I can't earn this again, this is a meaningful part of my financial retirement solution and I need to know how this meshes with my money life outside investment properties and whatever else.

"When your accounts are small you look at your account as if it's a saving account almost - and who needs advice on a savings account? But at some point it's not a savings account any more it's an investment account. Then you think to yourself 'you know what I need a strategy'.."

He said after about 15 years in the scheme people would often find their investments were delivering more returns than they were contributing themselves, which would be a tipping point for how they thought about the scheme.

At Milford, head of KiwiSaver Murray Harris said people moving to it were often bringing established balances.

"But the main thing is the latest figures I saw 76 percent of our members are contributing to their accounts, which is high. If you look at other providers, default providers, they have numbers as low as 30 percent or 40 percent."

He said about 20 percent of members had taken some form of advice and often might be contributing more than the average 3 percent.

The average age of members was 44.

MJW noted that fees and expenses rose to a new record of $783 million in the year.

Part of that was due to an increase in asset balances but MJW said it could also reflect the movement of people towards higher fee active providers such as Milford, Generate and Booster.

Fees paid by the average member reached $238 per member.

"Default providers have, on average, $149 in fees and expenses per member, while non-default providers are about twice that at $297. Note that not all members within a default provider's scheme are default members," MJW said.