Offset account vs extra repayments: which actually saves more?
Here's the surprise: at the same interest rate, a dollar in offset and a dollar of extra repayment save exactly the same interest. The choice is about everything else.
Interest-wise, they're twins. Interest is charged on (loan balance − offset balance) with an offset, or on the reduced loan balance with an extra repayment - the same subtraction either way. A dollar in either place stops the same interest. The differences are practical, not mathematical.
Where offset wins
Access. Offset money is spendable today - no redraw request, no limits, no waiting. That makes it the natural home for an emergency fund or savings you'll eventually use. Flexibility with intent: salary can land in offset and chip at interest daily (lenders calculate daily, per MoneySmart) even if you spend most of it through the month.
Where extra repayments win
Cost. Offset features often come with package fees or a slightly higher rate; basic loans with free extra repayments avoid that. Discipline. Money in the loan is harder to impulse-spend than money sitting in what looks like a transaction account - for some people that friction is the feature. Availability: extra repayments work on almost any loan; full offset generally needs a variable-rate loan that offers it.
A fair rule of thumb: money you might need → offset. Money you're certain is going to the house → either works, so let fees decide. Small balances (MoneySmart suggests roughly under $10,000) may not justify offset package costs at all.
The calculator models extra monthly repayments and offset balances as separate inputs on the same simulation, so you can put the same dollars in each and watch the outcomes converge - or diverge once you account for what the feature costs you. The same page also lets you check your actual bank statement against the expected interest charge - most calculators only run the forward projection, not the reconciliation.
General information only. This page explains how a loan feature works mathematically - it isn't financial advice, doesn't consider your circumstances, and loan products differ. For guidance on your situation, consider a licensed adviser; for impartial basics, Australia's government-run MoneySmart is a good starting point.