Verified Customer Case Studies

Bottom line up front: a verified customer case study is a real Kiwi household where we have seen the actual power bills before and after solar, confirmed the install with the installer, and checked the numbers against the homeowner's lines company invoice. Not a glossy testimonial. Not a stock photo of a smiling family. The case studies we publish at NZ Solar Centre are anonymised by suburb (not by household), include the system size in kW, the verified pre-solar and post-solar bills in dollars, the install date, the retailer at the time, and the lines company. If a case study can't show those six things, we don't publish it. This page walks you through how we verify, what you can learn from real Kiwi homes, and how to use the patterns to sanity-check any quote you're handed.

This article sits inside our Trust Proxy promise to NZ homeowners. It's the part where we put our money where our mouth is. Anyone can claim "thousands of happy customers". Far fewer can show you the actual Genesis or Mercury bill from before, the post-install bill from after, and a system that matches what was sold.

If you're researching solar and you've been burned by sales talk, this is the article for you. We'll walk you through the verification process, share a few representative case study patterns from around Aotearoa, show you the common pitfalls in fake or cherry-picked testimonials, and give you a checklist you can use on any installer's website tomorrow morning.

What "Verified Case Study" Actually Means for NZ Homeowners

The solar industry in New Zealand has a long history of marketing-led storytelling. A homeowner is photographed in front of a sunny roof, a glowing quote sits beneath, and the implication is that everyone saves thousands. The problem is that almost none of those stories carry verifiable evidence. The bill might never have existed. The "85% reduction" might apply to a single sunny month in February.

A verified case study at NZ Solar Centre means a homeowner has supplied us with:

• Their pre-install retailer bills for at least 6 months (12 ideally), redacted of personal info but showing kWh usage and dollar totals
• Their post-install retailer bills for the same length of period
• A copy of the installer's commissioning paperwork, showing system size, panel model, inverter model, and install date
• The lines company (Vector, Orion, Powerco, Aurora, WEL Networks, Wellington Electricity, Top Energy, etc.) confirming the export-capable ICP connection
• A current buy-back rate applied at the time of measurement, cross-referenced against the retailer's published rate
• The homeowner's signed consent for us to publish the data, anonymised by household but identifiable by suburb and system size

If a case study can't tick those six boxes, it doesn't go on the site. That's the rule.

Why anonymity by suburb (and not by household) matters

We don't publish full addresses or surnames; that would breach the Privacy Act 2020 and frankly it's nobody's business. But we do publish suburbs because suburb-level data is useful for the next reader. A homeowner in Howick comparing solar wants to see verified savings from Howick, Pakuranga, or Botany; not from an unnamed "Auckland home". You can read more about how we handle this in our companion piece on how we protect your data under the Privacy Act 2020.

The Six Things Every Case Study Must Show

When you're scrolling an installer's website looking at testimonials, here's the mental checklist to run against every single one. If even one of these is missing, treat the testimonial as marketing fluff, not evidence.

1. System size in kW (e.g. 6.6 kW PV with 10 kWh LiFePO4 battery). Without this, you can't compare to your own quote.
2. Install date. A system installed in 2019 lived through different buy-back rates than one installed in 2024.
3. Suburb and lines company. Sun hours and line charges vary hugely across NZ.
4. Pre-solar annual bill in dollars, with the retailer named.
5. Post-solar annual bill in dollars, with the retailer named (sometimes the same, sometimes switched).
6. Annual buy-back credits received, separately from consumption savings. These are two different things and lumping them together is one of the oldest tricks in the book.

Most of the testimonials you'll see on competitor sites show one or two of these. A case study with all six is something you can actually learn from.

Representative Patterns From Verified Kiwi Homes

Below are three representative patterns we see across our verified case study library. These aren't promises, and your home will differ; they're real shapes of real results, anonymised. We've kept the dollar figures conservative and rounded, because exact retailer rates shift with each contract.

Pattern 1: Auckland family, 6.6 kW PV, no battery (East Auckland, Vector)

A four-person household in Howick with a typical 1990s brick-and-tile home, installed a 6.6 kW north-facing array in early 2023. They are on a standard Mercury anytime plan and were paying around $3,200 a year before solar.

After 12 months of operation, the household's consumption from the grid roughly halved. They drew their morning and evening peaks from the grid and exported their middle-of-the-day surplus. The combined result, savings on consumption plus buy-back credits, came to a verified reduction of approximately 45-55% on their annual bill. Not 90%. Not "near zero". A solid, real, repeatable mid-40s percentage reduction.

The lesson: a no-battery system in Auckland on a flat tariff will typically halve, not eliminate, your annual bill. Anyone promising more should be asked to show the maths.

Pattern 2: Tauranga retiree couple, 5 kW PV + 10 kWh battery (Bethlehem, Powerco)

A retired couple in Bethlehem installed a 5 kW array with a 10 kWh LiFePO4 battery in late 2022. They're home during the day, which changes the maths considerably; they self-consume far more of what they generate, and the battery covers most of their evening usage.

Their pre-solar bill sat around $2,400 per year. Post-install, their grid draw dropped substantially and their buy-back credits were modest (most of what they produce, they use). Their verified bill reduction was approximately 65-75% across a full year.

The lesson: retirees and work-from-home households see the strongest ROI from solar plus battery, because they self-consume during peak generation hours. You can run your own numbers through our Solar System Cost & ROI Calculator to see how your daytime occupancy affects the picture.

Pattern 3: Christchurch family with an EV, 8.8 kW PV + 13.5 kWh battery (Halswell, Orion)

A young family in Halswell with one EV and a second car about to be replaced. Installed 8.8 kW of PV and a 13.5 kWh battery in 2023. They moved to a time-of-use plan and charge the EV during the solar generation window where possible.

Pre-install combined power and petrol costs (the petrol they used to put in the now-retired second car) were around $5,800 a year. Post-install, with EV charging shifted to solar hours and the second car gone, their verified annual energy spend dropped by roughly 60%.

The lesson: solar plus EV plus a smart tariff is where the maths gets exciting. The savings aren't just on the power bill; they're on the petrol bill too. Pair this with a retailer on a dynamic tariff and the picture improves further (we keep live rates updated in our Dynamic Tariff & Buy-Back Engine).

What This Means for You

If you're an ROI Pragmatist

Use verified case studies as the calibration tool for your own quote. When an installer hands you a "you'll save $X per year" estimate, look for a verified case study in your suburb (or a comparable one) and a comparable system size. If the installer's promise is dramatically rosier than the verified pattern, ask why.

Also check the system size to bill ratio. A 6.6 kW system on a $2,000-a-year house behaves very differently to a 6.6 kW system on a $4,500-a-year house. Bigger bills generally have more room to save, but only if your daytime usage pattern fits.

If you're a Tech-Savvy Optimiser

The case studies that matter to you are the ones showing the full hardware spec: panel make and model, inverter make and model, battery chemistry and brand, and the retailer/tariff combination. Without those, you can't reverse-engineer whether the result is from a great install or a great tariff (or both).

Pay particular attention to case studies where the homeowner is on a dynamic or time-of-use tariff. That's where the optimiser's playbook delivers, and where a great inverter (Sungrow, Fronius, GoodWe, Enphase) paired with smart EV charging multiplies the effect.

If you're an Eco-Conscious Family

Look beyond dollars. The verified case studies we publish also show estimated CO2 offset based on the household's grid mix at the time. They show how many years the family has been running without issue (longevity is a sustainability story too) and whether the LiFePO4 battery has any reported degradation.

For your family, the case study is also a comfort check. Real Kiwi families running real systems for years without drama tells you the technology works. It's not experimental; it's mature.

What Installers Won't Tell You About Their Case Studies

The kind way to put this is that the industry has been "selective" with its storytelling. The blunt way to put it is that some installers cherry-pick, exaggerate, or simply invent. Here are the patterns we've seen, and what to watch for.

• "Saved 90% on their power bill!" Almost always this is a single summer month, not an annual figure. Annual savings for a typical no-battery system are closer to 35-55%.
• No system size mentioned. If the case study doesn't say whether it was a 3 kW or a 10 kW install, the numbers are meaningless to you.
• Buy-back credits counted as "savings". Buy-back is a separate income stream and depends entirely on your retailer. Conflating it with consumption savings inflates the headline.
• Old systems quoted at current rates. A 2018 install measured against 2024 power prices will look spectacular. Solar got cheaper; power got dearer. The maths is artificially flattering.
• "Bill went from $400 to $30 a month!" Was that summer? Winter? An average? Without 12 months of data, the comparison isn't honest.
• Stock photos instead of the actual home. A red flag, but not a deal-breaker on its own. The deal-breaker is when the bill figures are also vague.
• No suburb, no lines company. Auckland and Invercargill see massively different sun. A case study that doesn't anchor geographically isn't useful.

If you spot two or more of those patterns on an installer's testimonial page, treat their savings claims with healthy scepticism. Our Solar Scam Checklist covers the broader warning signs in detail, and our 13-Step Installer Vetting Process shows how we screen for installers who don't play these games.

How We Source and Verify Each Case Study

For transparency, here's the actual workflow we use when a homeowner offers to share their story with us.

1. Initial intake. Homeowner contacts us (usually after they've used the site for a while). We send a verification request listing the six required pieces of evidence.
2. Document collection. Homeowner uploads bills (redacted of personal data), commissioning paperwork, and ICP confirmation through a secure form covered by our Privacy Act 2020 process.
3. Cross-checking. We contact the named installer to confirm the install actually occurred and matches the paperwork. We check the retailer's published buy-back rate at the time against what appears on the bill.
4. Sense-check the maths. We model what we'd expect the system to produce in that suburb using NIWA irradiance data and the panel orientation supplied. If the homeowner's claimed savings are more than 15% above the modelled expectation, we ask follow-up questions before publishing.
5. Anonymisation. Suburb stays; surname and street address go. We re-issue the case study to the homeowner for final sign-off before it goes live.
6. Annual refresh. Every twelve months, we ask the homeowner if they're happy to share a fresh bill snapshot, so the case study reflects current performance, not a one-off year.

It's slow. It's why we publish far fewer case studies than the average installer's website claims to have. But every single one is real.

Frequently Asked Questions

How many verified case studies do you have?

The library grows steadily. We add cases only as they pass the six-point verification, so the number is deliberately modest. Quality over quantity; one verified case is worth a hundred testimonials.

Can I submit my own home as a case study?

Yes, and we'd love that. Reach out through the contact form. You'll need access to your pre-install and post-install bills, your installer's commissioning paperwork, and a willingness to share suburb-level data. We anonymise everything else.

Why don't you publish full names or addresses?

Privacy Act 2020 obligations, primarily. But also: most homeowners aren't comfortable advertising the value of solar gear on their roof. Suburb-level data gives readers what they need without exposing the homeowner.

Are your case studies independent of installers?

Yes. We don't publish a case study because an installer asked us to. The homeowner is our point of contact; the installer simply confirms install details. We have no commercial relationship that would require us to favour any particular brand or installer.

How do I tell if a competitor's case studies are real?

Run the six-point checklist: system size, install date, suburb and lines company, pre-solar annual dollar figure, post-solar annual dollar figure, separate buy-back income. If even one is missing, treat it as a marketing piece, not evidence.

Will my system perform like the case studies I read?

Maybe within a reasonable range, but every home is different. Roof orientation, shading, daytime occupancy, retailer, lines company, and your appliances all shift the maths. Use case studies as patterns, then run your specific numbers through our ROI Calculator for a quote-comparable estimate.

Why don't you publish "best case" results?

Because best-case results mislead. We deliberately publish representative results and label clear outliers as outliers. A "saved 92% in February" headline tells you nothing about your annual bill. We'd rather under-promise and be useful than over-promise and lose your trust.

How recent are the case studies?

Each is dated by install year and we refresh the bill data annually where the homeowner is willing. The market changes (buy-back rates, panel prices, retailer plans) so an old case study, while still real, may not reflect current returns. We flag this on each entry.

Where to Go From Here

If you've made it this far, you're doing the homework most homeowners skip. The next sensible step depends on where you're at in your journey. If you're still building your understanding of how an installer should behave, read our 13-Step Installer Vetting Process. If you want to stress-test a quote you've already received, our Solar Scam Checklist is the tool. And if you want to know what the numbers might look like on your specific roof, the Solar System Cost & ROI Calculator is the fastest way to get a grounded estimate.

For the bigger picture of how all of this fits together (the verification, the vetting, the privacy commitment, the case studies), our Trust Proxy promise is the parent page that ties the whole approach together.