Guide to the BNZ Green Home Loan

If you bank with BNZ and you're putting solar on your roof, the BNZ Green Home Loan lets you borrow up to $80,000 at a fixed 1% p.a. for the first three years to pay for solar panels, batteries, and a list of other energy-efficiency upgrades. That 1% rate is the headline, and it's genuinely one of the lowest pieces of consumer lending available in New Zealand right now. On a typical $13,000 solar-and-battery spend, the difference between 1% and a standard 12% personal loan is roughly $2,000 to $2,500 in interest saved over three years. The catch worth knowing up front: it's a top-up on an existing BNZ home loan, so you need a mortgage with them and enough equity, and after the three-year sweetener the rate reverts to a standard home-loan rate.

What the BNZ Green Home Loan actually is

It's not a separate product you apply for on its own. It's an add-on (a top-up) to an existing BNZ home loan. You're borrowing against your house, at a special low rate, for approved green purchases. That structure matters because it shapes who can use it and how the maths works out.

BNZ has run this since 2021. The core terms, per BNZ's own published lending information, are:

• Up to $80,000 borrowable for qualifying green upgrades.
• 1% p.a. fixed for the first 3 years on the green portion.
• After 3 years it rolls onto a standard home-loan interest rate of your choosing (fixed or floating, whatever's going at the time).
• No establishment or top-up fee on the green lending itself.
• You need to be an existing BNZ home-loan customer (or taking one out) with the equity to support the extra borrowing.

Solar panels and home batteries are both on BNZ's approved list, alongside things like insulation, double glazing, heat pumps, and EV chargers. That breadth is the quietly useful bit, and we'll come back to it, because it changes how you should think about a solar project.

Why the 1% rate matters more than most people realise

Most solar finance in New Zealand sits somewhere between a personal loan and a hire-purchase arrangement, and the rates are not gentle. Unsecured solar finance commonly runs 9% to 13% p.a., and some of the "interest-free" deals carry hefty admin or account fees that drag the real cost up. We pull the true cost of these arrangements apart properly over here: https://nzsolaris.co.nz/the-true-cost-of-going-solar-in-nz-bills-finance-and-roi/.

At 1%, the interest almost stops mattering. Here's the difference in plain numbers on a $13,000 solar-and-battery system repaid over three years:

• At 1% p.a. (Green Home Loan): roughly $200 total interest over three years.
• At 12% p.a. (typical unsecured solar loan): roughly $2,500 total interest over three years.

That's a real-world saving of around $2,300, and it's the part that genuinely shifts the payback equation. When you finance solar at 10% or more, a chunk of your power-bill savings goes straight back out the door as interest. At 1%, almost all of your savings stay in your pocket. For a lot of households this is the difference between solar that pays for itself comfortably and solar that just treads water.

If you want to sanity-check whether the system itself stacks up before you even think about finance, we go through the real return on investment for NZ homes here: https://nzsolaris.co.nz/are-solar-panels-worth-it-nz/.

Combining solar and a battery in the one loan

This is where the Green Home Loan gets genuinely interesting, and where it beats a lot of installer finance. Because batteries are on BNZ's approved list alongside panels, you can fund the whole job, panels plus storage, on the same 1% lending.

That's a bigger deal than it sounds. Batteries are the part of a solar project where the payback maths is hardest. A home battery in 2025 typically adds $8,000 to $15,000 to a job depending on size, and on its own a battery often takes well over a decade to pay back at current power and buy-back rates. Financing that at 12% would usually kill the case entirely. Financing it at 1% is a completely different conversation.

The trap nobody warns you about: borrow for the battery, not the panels

Here's a piece of maths the installers won't volunteer, and it's the single most useful thing to take away.

If you can only get part of your project onto the 1% lending (because of equity limits, or because you've got cash for some of it), put the 1% borrowing against the battery, and pay for the panels with cash if you can.

Why? Because solar panels generate savings from day one and pay themselves back fast, often inside 6 to 9 years. They carry interest well. A battery, by contrast, is the slow earner, and it's the part that benefits most from near-zero-cost money. The lowest-cost finance should always sit against the asset with the longest payback. Most people do it backwards, financing the "exciting" panels and paying cash for the battery, and they leave money on the table doing it.

It makes no practical difference to BNZ which part of the bill the loan notionally covers. It makes a real difference to your wallet.

A worked example: a Tauranga family doing the full job

Picture a 2000s brick-and-tile place in Pyes Pa, Tauranga, on the Powerco network. The owners want a 6.6kW system with a 10kWh battery. The installed price comes in at $22,000 all up, which is in the right ballpark for that size of job in 2025 (you can check current per-watt pricing here: https://nzsolaris.co.nz/cost-per-watt-nz/).

They've got a BNZ mortgage and plenty of equity. They top up $22,000 on the Green Home Loan at 1% for three years.

• Repayments: roughly $620 a month over three years to clear it inside the 1% window.
• Total interest at 1%: around $340 over the three years.
• What the same loan would cost at 12%: around $4,300 in interest.

So the Green Home Loan saves this household close to $4,000 over a job they were going to do anyway. Their solar and battery start offsetting power bills immediately, and because the borrowing is so low-cost, the bill savings comfortably outrun the repayments for most of the year.

The honest footnote: $620 a month is real money, and it's higher than a longer-term loan would be. That's deliberate. To actually capture the 1% benefit you want the bulk of it repaid before the three-year fixed period ends and the rate reverts. Which brings us to the catch.

The catch worth understanding: what happens after three years

The 1% rate is fixed for three years only. After that, the green portion rolls onto a standard BNZ home-loan rate, whatever that is at the time. In recent years standard home-loan rates have sat anywhere from the mid-2% range up to the mid-7% range, so the reversion is not trivial.

There are two sensible ways to handle this:

• Clear it inside three years. Set your repayments to wipe the green portion before the rate reverts. This captures the maximum benefit. For a $13,000 job that's roughly $370 a month; for a $22,000 job, around $620 a month.
• Let it roll into your mortgage. If you can't clear it in time, the leftover simply becomes part of your ordinary home loan at the ordinary rate. That's not a disaster, but it's no longer special, and you'll pay normal mortgage interest on it, often for years.

The danger is treating the 1% as a 25-year giveaway. It isn't. It's a three-year head start. Plan your repayments around that window or the benefit quietly evaporates.

The hidden cost most people forget: securing it against your house

Here's the part that doesn't show up on the BNZ marketing, and it's worth thinking through honestly.

Because this is a mortgage top-up, the solar system is secured against your home. That's what makes the 1% rate possible: BNZ is taking very little risk. But it also means that if you stretch the repayment out across your whole mortgage term rather than clearing it quickly, a $13,000 system financed over 25 years at mortgage rates can quietly cost you far more in total interest than the panels ever save you.

This is the same trap that catches people who fold renovations into their mortgage and forget about them. The 1% three-year rate is excellent. The 25-year tail attached to it is where good intentions go to die. Pay it like a short loan, not like part of the house.

Who this works brilliantly for, and who should look elsewhere

The Green Home Loan is close to unbeatable if you:

• Already bank with BNZ and have a home loan with them.
• Have enough equity to support an extra $13,000 to $80,000 of lending.
• Can comfortably afford to repay the green portion within three years.
• Want to fund a battery, where the low-cost money matters most.

It's the wrong tool, or simply unavailable, if you:

• Don't have a mortgage with BNZ. You'd need to refinance your whole home loan across to get it, which only makes sense if BNZ's broader mortgage terms suit you anyway. Don't move your entire mortgage just to chase a solar rate.
• Are a renter, or don't own the roof. No mortgage, no top-up. Worth knowing the other big banks (ANZ, ASB, Westpac, Kiwibank, Co-operative Bank) run their own green or sustainable home-loan top-ups on broadly similar terms, so if your bank isn't BNZ, ask yours the same questions.
• Can't clear it inside three years. You'll still benefit, but less, and you need to be honest with yourself about the long tail.
• Want zero upfront cost with no borrowing at all. That's a different model entirely, and the subscription-style options have had a rocky run in NZ; we cover what happened to that market here: https://nzsolaris.co.nz/solarzero-subscription-alternative/.

How to actually set it up the smart way

The order of operations matters. Do it like this:

1. Get your solar quotes first, finance second. Know exactly what you're spending before you talk to the bank. A vague "around twenty grand" leads to vague borrowing. We can line up three quotes from vetted installers so you've got real numbers in hand: https://nzsolaris.co.nz/get-solar-quotes/.
2. Check your equity and approval informally. Talk to BNZ about how much green lending your equity supports before you commit to a system size. There's no point speccing a $30,000 setup if your top-up tops out at $20,000.
3. Decide your repayment plan around the three-year window. Work out the monthly figure that clears the green portion in 36 months and make sure it's genuinely affordable. If it isn't, scale the project to what is.
4. Apportion the 1% to the battery. If you're part-cash, part-finance, point the low-cost lending at the storage and the longest payback.
5. Keep the green portion visible. Ask BNZ to track it separately rather than blending it invisibly into the mortgage, so you can actually see it shrink and clear it on time.

If you'd like a quick gut-check on whether you qualify for green finance before you ring the bank, there's a simple tool for that here: https://nzsolaris.co.nz/green-finance-qualifier/.

Frequently asked questions

Can I use the BNZ Green Home Loan for a battery on its own?

Yes. Home batteries are on BNZ's approved green list, so you can fund storage with or without panels. Given a battery is the slowest part of a solar project to pay back, the 1% rate is arguably most valuable when it's pointed at storage.

Do I have to be a BNZ customer already?

You need a BNZ home loan to access the top-up. If you bank elsewhere, you'd have to move your mortgage across, which rarely makes sense just for a solar rate. Check whether your own bank offers a comparable green top-up first, since most of the big NZ banks now do.

What's the maximum I can borrow?

Up to $80,000 for qualifying green upgrades, per BNZ's published terms, subject to your equity and serviceability. That ceiling is generous enough to cover panels, a battery, an EV charger, and other efficiency work in one hit.

Is the 1% rate really fixed for the whole loan?

No, and this is the key thing to understand. The 1% is fixed for the first three years only. After that, the green portion reverts to a standard BNZ home-loan rate. Plan to repay it within the three-year window to capture the full benefit.

Are there fees?

BNZ does not charge an establishment or top-up fee on the green lending itself, per their published information. Always confirm the current terms directly with BNZ, since bank conditions change and your own situation may carry other costs.

Does securing the loan against my house put my home at risk?

It's secured lending, the same as any mortgage borrowing, so the usual rules apply: keep up the repayments and you're fine. The bigger practical risk isn't losing your home, it's letting the borrowing drift across a 25-year mortgage tail and paying far more interest than the solar ever saves. Repay it like a short loan.

Can I pay it off early without penalty?

Floating portions can generally be repaid early without break costs, and many people set up the green top-up to allow exactly that. Fixed portions can carry break fees, so confirm the structure with BNZ when you set it up, and ask specifically how to clear it inside three years cleanly.

Will solar plus this loan eliminate my power bill?

No. A grid-tied home in New Zealand still has fixed daily charges and draws power on dark winter evenings, so you'll always have a bill. What good solar does is cut that bill substantially, and low-cost finance means more of the saving stays with you rather than going to interest. Anyone promising a zero bill is overselling it.

The bottom line

The BNZ Green Home Loan is one of the genuinely good deals in NZ solar finance, provided you treat it as a three-year sprint rather than a 25-year stroll. The 1% rate can save you a couple of thousand dollars on a panel-only job and several thousand on a full panel-and-battery setup, and it's the single best way to make a home battery pencil out at today's prices. The smart move is to aim the low-cost money at the battery, repay the lot inside three years, and never let it quietly fold into the mortgage and grow a long tail of ordinary interest.

What to do next

Before you talk finance, get the system numbers right. It's worth understanding what a fair installed price looks like on your roof and whether the whole thing stacks up for your household in the first place. Once you've got real quotes in front of you, the BNZ conversation becomes simple maths instead of guesswork.

So the order is straightforward: nail down a real quote first, check your equity with BNZ second, then set your repayments to clear the green portion inside the three-year window. Do those three things and you'll capture the full benefit of the 1% rate without any nasty surprises down the track.