How long do solar panels last, and what fails first
By Daniel Carmont, licensed electrical contractor Lic# 92489
Nuvolt Electrical Solutions · 16 October 2026 · 8 min read
The honest short answer is that a decent solar panel installed properly will still be doing useful work in twenty five years, and quite probably longer. The panels are the most reliable part of a solar system by a wide margin.
I am a licensed electrical contractor on the Sunshine Coast (Lic# 92489) and an accredited solar installer, and most of my experience of old solar is being called out to systems that have stopped working. It is almost never the panels.
This article explains what the warranty numbers actually mean, what genuinely shortens a panel's life, and what to look at if you think yours are finished.
What a performance warranty actually promises
Panel warranties come in two parts and people routinely confuse them.
The product warranty covers the panel failing through a defect in materials or workmanship. On the panels we install that is 25 years.
The performance warranty is the interesting one. It does not promise the panel keeps making its rated power. It promises the panel will not fade faster than a stated rate. A typical modern promise is at least 97% of rated output in the first year, then no more than about 0.4% a year after that.
Run that out and it means a panel still has to be making at least about 87% of its nameplate power in year 25. Some of the panels we install carry that promise out to 30 years.
So a 30 year performance warranty is not a claim that the panel lasts exactly 30 years and then stops. It is a floor under how fast it is allowed to get worse, for 30 years. The panel does not expire at the end of it.
Degradation is slower than the scare stories
A fade of 0.4% a year is hard to picture, so here it is in practical terms.
A panel making a given amount of power today will be making roughly 96% of that in ten years and roughly 92% in twenty. That is the warranted floor, and real panels commonly do better than the floor because manufacturers set it conservatively.
For a household, that difference is genuinely small. It is far smaller than the difference between a clean array and a dirty one, smaller than the difference a shading problem makes, and vastly smaller than the effect of a system that has been sitting switched off for a month because nobody noticed the inverter had faulted.
If your generation has dropped noticeably, it is not degradation. Degradation does not produce a noticeable drop. It produces a barely measurable one over a decade. Something else is wrong, and it is worth finding out what.
The panels are rarely what fails first
In practice, the order things go wrong is fairly consistent, and the panels are near the end of it.
The inverter is the usual answer. It is the component with the hardest job, doing constant high frequency switching, often mounted somewhere hot, and it carries a shorter warranty than the panels for a reason. Most systems will need an inverter replaced before they need a single panel replaced.
DC isolators are the classic Australian failure. The rooftop isolator sits in weather and UV for years, and a cracked isolator, or one with water inside it, is one of the most common faults we find, and one of the genuinely dangerous ones.
Then connectors and cabling, particularly where mismatched connectors have been pushed together or cable has been left resting on a roof sheet to chafe.
Then the panels, usually not failing outright but developing microcracks or, occasionally, backsheet degradation on older panels with a plastic rear layer. We wrote about the full pattern in what actually fails on a solar system after ten years.
What actually shortens a panel's life
Heat, more than anything. Panels run hotter than people realise and heat drives every ageing process in them. It is also why a panel mounted with proper air gap behind it does better than one clamped tight to a hot surface.
Flexing. A panel that moves in wind develops microcracks in the cells. Those do not announce themselves: the system keeps running and quietly makes less. Frame stiffness and correct clamping both matter here, which is why the mounting is not the place to save money.
Salt air, which is our local speciality. It attacks frames, fixings and anything not properly rated, and it is the reason solar on coastal homes needs different hardware rather than the same kit used inland.
Water ingress, usually through a failing backsheet on older panels or a damaged junction box. Panels with glass on both sides rather than a plastic backsheet remove that failure mode entirely.
And bad installation, which is the big one nobody lists. Clamps done up too tight, panels mounted on the wrong part of the frame, penetrations that were never sealed properly. A good panel installed badly will not reach its warranty; a middle of the range panel installed properly will sail past it.
How to tell if yours are actually past it
Start by ruling out everything cheaper. Check the inverter is actually running and not sitting on a fault. Check the array is not filthy, because on the Sunshine Coast a season of dust, salt and bird mess is worth more lost output than a decade of degradation. Check nothing has grown into the sun since the system went in, because a tree that was small in 2015 is not small now.
If the system genuinely is underperforming after that, the honest diagnostic is a look at the panel level, not a guess from the total. A string that is down while its neighbour is fine tells you where to look, and thermal imaging will show a cracked cell or a hot connection that no amount of reading the app will find. Thermal imaging is the tool for that.
And a practical note on old systems: if your panels are from the early 2010s and something has failed, the question is usually not whether to repair the panels. It is whether the money is better spent on a modern array, since today's panels make far more power per square metre of roof. A roof that fitted 4 kW in 2013 will often take double that now.
If you want an honest opinion on whether a system is worth keeping, that is exactly the sort of thing our preventative maintenance checks are for.
Common questions
How long do solar panels actually last?
A decent panel installed properly will still be doing useful work at twenty five years and quite probably longer. Modern panels carry a 25 year product warranty and a performance warranty of 25 to 30 years, and the panel does not stop working at the end of that. Panels are the most reliable part of a solar system.
What does a 30 year performance warranty on a solar panel mean?
It is not a promise the panel lasts 30 years. It is a floor on how fast it is allowed to fade: typically at least 97% of rated output in year one, then no more than about 0.4% a year, so it still has to make roughly 87% of its nameplate power at the end of the term. Real panels often do better, because the floor is set conservatively.
My solar generation has dropped. Is it panel degradation?
Almost certainly not. Degradation runs at a fraction of a percent a year, which is far too slow to notice. A noticeable drop means something else: an inverter sitting on a fault, a dirty array, new shading from a grown tree, a failed DC isolator or a string that has dropped out. It is worth finding out which.
What fails first on a solar system?
Usually the inverter, which has the hardest job and the shortest warranty. Then DC isolators, which sit in weather and UV and are a common and genuinely dangerous Australian failure. Then connectors and cabling. The panels themselves are near the end of that list.
Is it worth replacing old solar panels?
If the panels are from the early 2010s and something has failed, the question is usually whether to replace the array rather than repair it. Modern panels make far more power per square metre, so a roof that fitted 4 kW a decade ago will often take double that now. The economics usually favour a new array over patching an old one.
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