HomeSolar panels do not really “last twenty-five years” and then stop. They fade. A panel at year thirty is still producing — just less than it did new. Understanding that changes what the warranty means and what you should actually worry about.
Degradation, which is the real answer
A solar panel loses a small fraction of its output every year. Modern modules typically degrade at somewhere around 0.3% to 0.5% annually, often with a slightly larger drop in the first year as the cells stabilise.
Compound that and the picture is reassuring. At roughly 0.4% a year, a panel is producing somewhere in the high eighties as a percentage of its original output after twenty-five years. That is the basis of the standard performance warranty, which typically guarantees around 85% to 90% of rated output at year twenty-five depending on manufacturer and tier.
So the honest answer to “how long do they last” is that the panels are the most durable part of the system and will very likely outlive their warranty. Which is why the more useful question is what breaks first.
Two warranties, and people conflate them
Every panel comes with two, and they cover different things:
- The product warranty covers manufacturing defects — delamination, junction box failure, frame problems. Commonly 12 to 25 years depending on tier. This is the one that replaces a physically faulty panel.
- The performance warranty guarantees the panel still produces a specified percentage of rated output at specified years. This is the “25-year” figure usually quoted.
A panel can be within its performance warranty and still be broken, and vice versa. When comparing quotes, ask for both numbers rather than accepting “25-year warranty” as a single fact.
And there is a third, separate from the equipment entirely: the workmanship warranty from whoever installed it, covering the racking, the flashing and the electrical work. On a New York flat roof this is arguably the one that matters most, because a leak at a penetration will cost you more than a degraded panel ever will. Ask how long it runs and what it covers.
The inverter is what actually fails
This is the practical answer to “what breaks first,” and it is almost always the inverter.
String inverters — one central unit converting the whole array — typically carry warranties around 10 to 12 years, sometimes extendable. Expect to replace one at least once during the panels’ life. It is a known, plannable cost, not a disaster.
Microinverters and DC optimisers — module-level electronics, one per panel — generally carry warranties in the 25-year range, matching the panels. They cost more up front and are the right choice on shaded or complex roofs because each panel operates independently.
There is a genuine tradeoff and it is not obvious. A string inverter puts one accessible box at ground level that a technician can swap in an afternoon. Module-level electronics are on the roof, under the panels — longer warranties, but a failure means going back onto the roof and partially dismantling an array to reach one unit.
On a Brooklyn row house with hatch-only roof access, that access difficulty is worth weighing rather than treating the longer warranty as automatically better.
What New York weather actually does
Panels are tested to withstand hail, wind loading and thermal cycling well beyond ordinary New York conditions. The specific local stresses:
Freeze-thaw cycling. The most relentless one. Repeated freezing and thawing works at seals, junction boxes and every mechanical connection. It is the reason installation quality matters more here than in a mild climate — a marginal connection that would survive decades in California will find its limit in New York.
Snow. Rarely a structural problem; panels are rated for snow loads well above what the city gets. It costs you production while it sits, and it mostly slides or melts off tilted panels within days. A useful side effect: snow sliding off an array cleans it.
Heat. Counterintuitively, this costs more annual production than snow does. Panel efficiency falls as cell temperature rises, so peak summer output is lower than a spring day at the same irradiance. Good installations leave an air gap under the modules for exactly this reason — flush-mounting tight to a dark membrane runs hotter and produces less.
Salt air. Real for coastal Brooklyn, the Rockaways and southern Staten Island. It attacks fasteners, racking and flashings rather than the panels themselves. Marine-grade hardware is worth specifying near the water.
Soiling. City grime, pollen and bird droppings. Rain handles most of it on a tilted array. Where it becomes a real loss is under a tree, where sap and leaf litter accumulate faster than rain clears them.
The failure mode that actually costs New Yorkers money
Not weather. Not degradation. It is this: a solar system can fail silently for months and nothing in your house behaves differently.
Lights work. Appliances work. The only symptom is an electric bill higher than it should be — and bills vary seasonally, so it is easy to miss two or three of them before noticing something is wrong. Meanwhile an inverter has been offline since April.
This is why monitoring is not an accessory. Every modern system has production monitoring, usually through an app. Check it monthly against the same month last year. That comparison takes about a minute and constitutes the entirety of solar maintenance for most owners.
If production has dropped and it is not shading or soiling, it is nearly always an inverter or a single-panel electronics failure — both diagnosable remotely, both usually within warranty.
What this means over twenty-five years
A realistic picture of owning an array in New York City:
- Panels fade a few tenths of a percent a year and are still producing in the high eighties by year twenty-five.
- If you chose a string inverter, budget one replacement somewhere around year ten to fifteen.
- You check an app monthly and clear leaves occasionally.
- The roof underneath, if it was near end of life at installation, becomes the real problem — which is the argument for sorting the roof out first.
Note what is not on that list: cleaning contracts, annual servicing, or panel replacements. Solar is unusually low-maintenance, and companies selling annual maintenance plans on residential rooftop arrays are generally selling you something you do not need.
If you want to know what a system on your specific roof would realistically produce in year one and year twenty, including the temperature and shading losses that generic estimates skip, ask us for the modelled numbers — and ask whoever else you are talking to for theirs, so you can compare like with like.