Solar is a great investment when it’s bought well — and a disappointing one when it’s bought badly. The encouraging thing is that the mistakes people regret are nearly always the same handful, and every one of them is avoidable once you know to look for it. Think of this as the list of traps to sidestep before you sign. Get these right and you’ve avoided almost every common solar regret.
Mistake 1: Oversizing for export
The most frequent sizing error is buying a system far bigger than your daytime usage, on the assumption that “bigger is better”. It usually isn’t. Without a battery, all that extra generation just exports to the grid at the low buy-back rate (~10c) instead of saving you the full retail price (~39c) you’d get from using it. Avoid it by: sizing to your daytime self-consumption, not your total bill — and if your usage is mostly in the evening, looking at a battery or shifting usage rather than just adding panels. (See what size system do I need.)
Mistake 2: Chasing the cheapest quote
A rock-bottom price is tempting, but in solar, cheapest-up-front is often dearest-over-time. A bargain quote usually hides budget panels, a short-lived inverter, or a rushed install — costs that resurface as lost output, early replacements, and warranty headaches. Avoid it by: comparing on value, not just price — what panels and inverter, what warranties, what’s included — and treating a quote far below the others as a question, not a win. (See why cheap solar can cost more.)
Mistake 3: Ignoring the inverter
People fixate on the panels and barely glance at the inverter — yet it’s the component most likely to fail, the one that shapes performance on a shaded roof, and the part you’ll likely replace mid-life. A cheap, no-name inverter is a false economy. Avoid it by: asking what inverter is included, what type, what brand, and what warranty — and not letting it be an afterthought.
Mistake 4: Underrating the installer
The installer matters more than the panel brand, but buyers often choose on price or hardware and overlook who’s doing the work. A great panel poorly installed underperforms or fails; a solid panel installed well lasts decades. Avoid it by: vetting the installer — registered electrician, Certificate of Compliance, accreditation, a workmanship warranty, and good references. (See how to choose an installer.)
Mistake 5: Trusting rosy savings numbers
A salesperson quoting one big, round savings figure — or a suspiciously short payback — is a warning sign, because real savings depend heavily on your usage and self-consumption. Optimistic numbers set you up for disappointment. Avoid it by: asking how the savings were calculated, expecting a range with assumptions, and being sceptical of any “three-year payback” claim.
Mistake 6: Falling for fake urgency
“Today only” pricing, a closing “government rebate” (there isn’t a national one), or pressure to sign on the spot are all tactics, not genuine offers. Avoid it by: never signing under pressure, getting two or three quotes, and walking away from anyone manufacturing a deadline. (See solar sales red flags.)
Mistake 7: Skipping the homework on your own home
Finally, some regret comes from not understanding your own situation — your usage pattern, your roof’s shade, whether you’re home in the day. Solar that’s perfect for your neighbour may be mediocre for you. Avoid it by: understanding when you use power and what your roof can do before you buy, so the system is matched to your home.
The verdict
Almost every solar buying regret traces back to the same avoidable mistakes: oversizing for export, chasing the cheapest quote, ignoring the inverter, underrating the installer, trusting rosy savings figures, falling for fake urgency, and not understanding your own usage. None of them require expertise to dodge — just knowing they exist. Size to your usage, judge on value and the installer, demand honest numbers, never buy under pressure, and you’ll land on the right side of the line where solar is the sound investment it should be.
Get a free assessment for honest, independent numbers before you commit.
Sources: Common buying pitfalls per NZ consumer and industry guidance (2026); pricing, payback, and export ranges per EECA and the Electricity Authority. Figures vary by home.