If you're a borrower or a lender the website www.interest.co.nz should be useful to you.
You can find out quite a lot about what the banks are offering and you can compare banks. You can also use their calculator.
An investor, for example, can compare a PIE investment at one bank with a term deposit at another. If you wanted to reinvest interest as you go, you could work out what you could earn over the term of the loan.
Similar calculations can be made by borrowers.