The Dynamic Tariff & Buy-Back Engine

The Dynamic Tariff & Buy-Back Engine is a live comparison of what every major New Zealand retailer pays you for the solar power you export to the grid, paired with a quick calculator that turns your system size into a realistic dollar figure. Buy-back rates in 2025 swing wildly: from around 7 to 8 cents per kWh on the lower end up to 17 cents or more per kWh on the best flat plans, with some time-of-use deals paying a premium when the grid is short. That spread is the single biggest lever on your solar payback that almost nobody talks about at the point of sale. Plug in your details and you will see, in plain numbers, which retailer actually rewards your panels.

What this does for you

Most people choose a solar system carefully and then leave money on the table by staying on whatever electricity plan they already had. The buy-back rate, the price your retailer pays for the kilowatt-hours you push back to the grid, is set entirely by the retailer, not by your panels. Switch retailers and your export earnings can double overnight, with no change to your hardware.

So the tool does two jobs:

• Compares current buy-back rates across the retailers that actively court solar households, including Octopus Energy NZ, Ecotricity, Meridian, Contact, Genesis, Mercury and the smaller players worth knowing about.
• Estimates your annual export earnings based on your system size, your region's sun hours and a realistic split between what you use yourself and what you send back.

The result is a straight answer to a question quotes rarely address: once your panels are on the roof, which retailer leaves you best off?

What you'll need to use it

Nothing complicated. To get a sharp estimate, have these handy:

• Your planned (or installed) system size in kW. Most NZ homes land between 4kW and 8kW.
• Your region or postcode. This sets your expected annual generation. NIWA's solar radiation data shows a real spread across the country, and it matters more than people think.
• A rough sense of your daytime usage. Are you home during the day, or is the house empty until 6pm? This drives your self-consumption rate, which we explain below.
• A recent power bill (optional but useful). It tells you your current per-unit rate and your current buy-back, so you can compare apples with apples.

How it works, in plain English

Solar power you generate goes one of two places. You either use it on the spot (running the heat pump, the hot water cylinder, the dishwasher) or, if you are not using it right then, it flows out to the grid and your retailer pays you the buy-back rate for it.

That distinction is the whole game, and here is the part the industry tends to gloss over.

Self-consumption is worth far more than export

When you use your own solar power, you avoid buying a unit from the grid. In 2025 the average residential electricity price sits around 33 cents per kWh before fixed daily charges, according to MBIE's Quarterly Survey of Domestic Electricity Prices. So every unit you self-consume saves you roughly that much.

When you export instead, you only earn the buy-back rate, which on most plans is around half of what you pay to buy power. So a unit used at home is worth roughly twice a unit sold to the grid. The engine accounts for this. It does not pretend every kilowatt-hour you generate is worth the same, because it simply is not.

The logic underneath the numbers

For your estimated annual generation, we use regional sun-hour figures derived from NIWA data, so an Invercargill roof and a Nelson roof are not treated identically. We then apply a self-consumption assumption based on the daytime occupancy you tell us, and we value the rest at the buy-back rate of whichever retailer you are comparing. The output is two clear numbers: what you save by using your own power, and what you earn by exporting the surplus.

Why time-of-use plans complicate the picture

Here is something genuinely worth knowing. Octopus Energy NZ and a few others now offer plans where the buy-back rate changes through the day, sometimes spiking high when wholesale prices are up (cold winter evenings, dry-year shortages). On paper that looks fantastic. The catch: solar exports peak at midday, when grid prices are usually lowest. So a headline "up to" buy-back number on a time-of-use plan can be misleading for a solar household, because your panels are busiest at exactly the wrong time of day to capture the high rates.

This is precisely where a battery changes the maths: it lets you hold your midday surplus and export it (or use it) in the evening peak when both your usage and the buy-back rate are higher. The engine flags where a flat buy-back beats a time-of-use plan for a battery-less home, which is a comparison you will struggle to find spelled out anywhere else.

The honest limits of this estimate

We would rather you trust this tool than oversell it, so here is what it does not do.

• It gives you a solid planning estimate, not a guaranteed figure. Your actual generation depends on roof pitch, orientation, shading from that one neighbour's tree, and how grubby your panels get.
• Buy-back rates and plan terms change. We update the rates regularly, but always confirm the current offer directly with the retailer before you switch.
• Some retailers cap how much they will buy back, or pay a lower rate above a certain daily volume. We note these where they apply, but the fine print is the retailer's to confirm.
• It does not factor in fixed daily charges or sign-up credits, which can tilt the overall value of a plan. Read the whole offer, not just the buy-back number.

If some of these terms are new to you, we keep a plain-English rundown of the lingo over here: the NZ solar jargon buster. And once you know your export earnings, you can fold them into the bigger payback picture with our solar cost and ROI calculator.

What happens with your information

This is the heart of it, so we will be blunt. The engine runs on the numbers you enter to give you a result on screen. We do not require your name, your phone number or your address to use it, and we do not sell your details to a pack of installers who then hound you.

If you choose to take the next step and request quotes, that is a separate, deliberate decision you make, and we explain exactly how that works on our quotes page. Using the calculator on its own commits you to nothing. No spam, no on-selling, no obligation. That is a promise we keep because it is the only way this site is worth anything to you.

Why you can trust the numbers

We are independent and we sit firmly on the homeowner's side of the table. The rates and assumptions behind the engine come from named New Zealand sources, not guesswork:

• Retailer buy-back rates are taken directly from the published plans of each retailer and refreshed regularly. We treat this as the reference point our other guides point back to, so you are never reading a cents figure that quietly went stale two years ago.
• Generation estimates draw on NIWA solar radiation data for New Zealand regions.
• Average power prices come from MBIE's Quarterly Survey of Domestic Electricity Prices.
• Market and consumer context draws on the Electricity Authority and Consumer NZ, who both track retailer behaviour and plan switching.

It is free to use because the site is funded by a referral fee paid by vetted installers when a homeowner chooses to connect with one, paid by the installer, never by you. The tools stay free and open regardless of whether you ever request a quote.

A quick word on switching retailers

Changing electricity retailer in New Zealand is genuinely easy and usually free, and the Electricity Authority's own Powerswitch service exists to make it simpler. If the engine shows another retailer paying meaningfully more for your exports, the switch itself is typically a short online form and a few days' wait. Just check you are not locked into a fixed-term contract with an exit fee first, and weigh the buy-back rate against the buy price and daily charges together.

If you are also thinking about funding the system, it is worth seeing whether you qualify for a low-rate green loan before you commit, which you can check with our green finance qualifier.

Frequently Asked Questions

Is the engine really free?

Yes. There is no charge and no catch. You do not need to hand over personal details to see your numbers. The site is funded by referral fees from vetted installers, paid by them only if you choose to connect with one.

Do I have to give my contact details to use it?

No. You enter your system size, region and daytime usage to get a result on screen. Requesting quotes is a separate, optional step that you control.

How accurate is the export earnings estimate?

It is a solid planning estimate built on NIWA generation data and MBIE pricing, not a guarantee. Your real numbers depend on roof orientation, shading and your actual day-to-day usage. A proper site assessment will refine it.

Why do buy-back rates vary so much between retailers?

Because each retailer sets its own rate as a commercial decision. Some actively want solar customers and pay well; others pay the minimum. That is exactly why comparing them is worth your time, and why a switch can lift your export earnings with no change to your panels.

Is a high "up to" buy-back rate always the best deal?

Not necessarily. Some headline rates apply to time-of-use plans that pay the most in the evening peak, when your solar is no longer generating. Without a battery, a steady flat rate often earns a solar home more. The engine helps you see which suits your situation.

How often are the rates updated?

We refresh them regularly from each retailer's published plans, and we treat the figures here as the reference our other guides rely on. Always confirm the current offer with the retailer before switching, since plans can change between updates.

Will a battery change my numbers?

It can, significantly. A battery lets you store your midday surplus and use or export it during the higher-value evening peak, which improves both self-consumption and your effective return on time-of-use plans. The engine flags where this matters.

Does switching retailers cost anything?

Usually nothing, and it is typically a quick online process. Just check you are not in a fixed-term contract with an exit fee before you move. The Electricity Authority's Powerswitch service can help you compare and switch.

Does the estimate include my fixed daily charges?

No. It focuses on export earnings and self-consumption savings. Fixed daily charges and any sign-up credits affect a plan's overall value, so read the full offer, not just the buy-back cents figure.

What to do next

Here is the order that gets you the best result. First, run your system size and region through the engine and note your two numbers: your self-consumption savings and your export earnings. Then compare those export earnings across the retailers listed, and check whether a switch is worth your while given the buy price and daily charges as a package.

Before you commit to anything, run through this short list:

• Confirm the live rate with the retailer directly, since published plans can shift between our updates.
• Check for a fixed-term contract with an exit fee on your current plan before you move.
• Weigh the whole offer, not just the buy-back cents: buy price, daily charges and any sign-up credit all count.
• Match the plan to your home: a flat rate usually suits a battery-less household, a time-of-use plan can reward a home with a battery and evening usage.

Once you have your numbers sorted, fold them into the bigger picture with our solar cost and ROI calculator, and when you are ready for real pricing on your roof, the next step is just below.