Fixed vs Floating Mortgage Rate in NZ — Understanding the Decision

When you take out a mortgage in New Zealand, or when your fixed term comes up for renewal, you'll face a decision that gets asked constantly but is rarely answered well: should I fix, float, or split?

The default answer most people reach for — 'fix because rates are going down' or 'float because I want flexibility' — usually misses the real question. The right structure depends on your personal situation, your financial goals, and how your mortgage fits into your broader picture.

This article explains how fixed and floating rates work in the NZ context, what factors actually matter when choosing between them, and why this decision is more nuanced than it first appears.

What Is a Fixed Mortgage Rate?

A fixed interest rate is locked in for a specified term — commonly six months, one year, two years, or three years in the NZ market, though other terms are available. For the duration of that term, your interest rate stays the same regardless of what happens to market rates.

This certainty is the main appeal. You know exactly what your repayments will be, which makes budgeting straightforward. Fixed rates also protect you from rate increases during your term.

The trade-off is reduced flexibility. If you want to make significant extra repayments beyond what's permitted, sell your property, or switch lenders during a fixed term, you'll typically face a break fee. Break fees can vary significantly depending on the lender, the amount outstanding, and current market conditions.

What Is a Floating (Variable) Mortgage Rate?

A floating rate — sometimes called a variable rate — moves with the market. When the Reserve Bank of New Zealand (RBNZ) adjusts the Official Cash Rate (OCR), floating mortgage rates typically follow suit, though not always immediately or by the same amount.

The primary advantage of floating is flexibility. You can usually make unlimited extra repayments, restructure your loan, or exit without a break fee. This makes floating attractive for borrowers who may sell in the near term, who want to actively pay down their mortgage faster, or who need the ability to redraw funds.

The uncertainty is the obvious downside — your repayments can change. In a rising rate environment, floating becomes more expensive. In a falling rate environment, the opposite is true.

The OCR — Why It Matters to Your Mortgage

The RBNZ's Official Cash Rate is the benchmark interest rate for the NZ economy. It directly influences the interest rates banks charge on floating mortgages and broadly shapes the fixed rate environment through its impact on wholesale funding costs.

When the OCR rises, mortgage rates tend to rise. When it falls, rates typically follow. The RBNZ sets the OCR at regular review meetings throughout the year — these decisions are closely watched by anyone with a mortgage, particularly those on floating rates or approaching refix dates.

Understanding where the OCR is, where it's been, and where the market expects it to go provides useful context when thinking about fixed versus floating — though it's worth remembering that rate forecasts are just that: forecasts.

Split Lending — A Middle Path

One option many borrowers overlook is splitting the mortgage into portions — fixing some at different terms and leaving some floating. This approach lets you hedge your position: you get some certainty from the fixed portions and retain flexibility on the floating portion.

For example, a borrower might fix two thirds of their loan for different terms (to create a staggered refix schedule) and leave the remainder floating to allow for extra repayments or potential restructuring.

Split lending doesn't have to be an even split. The proportions should reflect your actual priorities — how much certainty you need, how much flexibility matters, and what you're planning to do with the property over the next few years.

What Actually Determines the Right Structure for You?

Rate expectations are one input into this decision — but they're not the only one, and arguably not the most important. Here are the questions that actually shape the right structure:

How likely are you to sell in the next one to three years? If there's a reasonable chance of selling, being locked into a long fixed term could expose you to a significant break fee.

Do you want to make extra repayments? If aggressively paying down principal is important to you, floating or shorter fixed terms give you more scope to do that.

How sensitive is your cash flow to rate movements? If a meaningful rate increase would cause real financial strain, the certainty of fixing has genuine value — independent of where you think rates are heading.

Are you an investor? Investment property lending often calls for a different structure than owner-occupied lending. Interest-only periods, how the loan interacts with your tax position, and refix timing relative to rental income cycles are all relevant considerations.

Why Rate-Chasing Isn't the Same as Strategy

The instinct to try to time rates is understandable — but it's worth recognising that most people, including professional economists, have a poor track record of predicting where rates will go. The RBNZ itself makes decisions based on incomplete and changing information.

A more useful frame is to build a loan structure that serves your actual situation well across a range of possible rate outcomes, rather than trying to optimise for a single predicted scenario. That's a more resilient approach — and it's the kind of thinking that tends to serve borrowers better over time.

Frequently Asked Questions