Why is my calculator result different from the bank's quote?

Let's break down the difference between the Break Fee NZ calculator and how banks actually do the math — in plain English.

1. Our method: The simple "Interest Difference"

Most of us calculate these things in a pretty straightforward way. The logic usually goes like this:

"I signed up at 6.5%, but now rates have dropped to 5.5%. That's a 1% difference. I have two years left on my contract, so I need to pay that 1% difference to the bank for those two years."

This is exactly how our website calculates it. The benefit is that it's simple and transparent. We use the "Retail Rate" (the rate you see advertised), so you can easily double-check the math on your own calculator.

2. The Bank's method: The complex "Cost Price"

Banks, however, look at a different set of numbers behind the scenes:

They look at "Wholesale Rates" (Swap Rates):
When banks calculate their loss, they don't look at the interest rate they sold to you. They look at what it cost them to borrow that money in the first place.

They look at "Present Value" (NPV):
Money in the future needs to be "discounted" to figure out what it's worth today.

3. Why does the website often show a higher price than the bank?

Usually, our website will give you a number slightly higher than what the bank actually charges. There are two main reasons for this "expensive estimate":

Reason 1: The "Discount" math (NPV)
As mentioned above, banks use a formula to discount future losses to today's value. Simply put: "A dollar next year isn't worth as much as a dollar in your hand today." Since you are paying the fee in one lump sum right now, the bank effectively gives you a small discount. Our simple calculator just adds it all up, so our number is naturally a bit higher.

Reason 2: Banks are fighting for customers (Profit Squeeze)
This is the real-world factor. Sometimes mortgage rates drop huge amounts, not because the bank's costs went down, but because the bank wants to steal customers from competitors, so they accept a smaller profit.

What you see: Mortgage rates dropped from 6.5% to 4.99%. Huge drop! The calculator sees this and thinks the fee will be high.
What the bank sees: Their actual costs only dropped a tiny bit. They are just cutting their own profit margin to offer a deal. When calculating your Break Fee, they can only charge you for their cost loss, not their profit loss.
The Result: The website thinks you have to pay a lot, but the bank only charges you for the small difference in their costs.

A quick note on NZ rules:
Under New Zealand regulations, banks aren't allowed to charge you for the profit they "would have made" if you'd stayed. They can only recover their actual funding cost — the real money they lost. So the fee is based on their wholesale loss, not their retail margin.

We keep this "slightly overestimated" method on purpose. It acts as a Safety Buffer. It ensures you are making decisions based on a conservative estimate.

4. When would the website be cheaper than the bank?

This is rare, but it can happen. If the wholesale market crashes (costs drop massive amounts) but the bank gets greedy and refuses to lower their mortgage rates, we have a problem.

In this case, our website looks at the mortgage rate and thinks "Oh, rates haven't changed much, no big fee." But behind the scenes, the bank's costs have dropped through the floor. In this specific scenario, the website might "underestimate" the fee.

However, in a competitive market like New Zealand, banks usually react pretty fast, so this doesn't happen often.

So What Now?

This calculator gives you a quick reference point — not the final answer. If the numbers look promising, it's probably worth a phone call to your bank to get an official quote. If it doesn't look great, at least you've saved yourself the hassle. Either way, you're making a more informed decision.