How Long Do Solar Panels Actually Last?

“25-year warranty” is printed on nearly every solar panel sold in India, and it is one of the most misunderstood numbers in the whole industry.

The warranty is a threshold, not an expiry date

A 25-year performance warranty guarantees that the panel still produces at least a stated share of its original rated output at that point — commonly somewhere in the 80-to-85% range depending on the manufacturer’s specific terms — not that it stops working the day after. Panels routinely keep generating usefully well past their warranty period, simply at a further, gradually reduced output.

Degradation is slow and steady, not a cliff

Output loss happens gradually, year on year, rather than in a sudden drop. A commonly used industry assumption is around 0.5% of output lost per year after a slightly larger first-year dip, though the exact figure varies by manufacturer and is stated on the panel’s own datasheet. This is not UTL-specific data — it is a standard assumption used across the industry when a manufacturer’s own figure is not otherwise available, and we say so rather than presenting it as a precise measured number for every panel we sell.

Why we show this assumption on every calculator result

A 25-year saving figure that hides its assumptions inside one big number is exactly the kind of thing that makes a solar calculator untrustworthy — the number looks impressive until someone asks “at what generation level, though?” Our calculator states the degradation and tariff-escalation assumptions used, plainly, next to the figure itself.

What actually shortens a panel’s useful life

Physical damage, poor mounting that lets water or wind stress the frame, and — as much as anything — extended dust buildup between cleanings (see our Punjab maintenance guide) affect real-world output far more than the panel’s own slow, natural degradation curve. A well-installed, reasonably maintained system tends to track close to its rated degradation curve for a very long time.

The honest summary

Twenty-five years is a warranty threshold worth understanding correctly, not a countdown to replacement. A panel bought today is a genuinely long-term asset, and the slow decline in output is a known, modest, already-priced-in factor in any estimate we give you — not a hidden catch.