Business leaders say workers could end up wearing the cost of KiwiSaver changes the National Party plans to bring in if it's re-elected in November.

The National Party plans to make KiwiSaver compulsory for all workers, if re-elected, as part of a suite of changes that would cost more than $1 billion over four years.

Making KiwiSaver compulsory and requiring a higher contribution rate should make New Zealanders better off at retirement - but can they afford to do it?