EN3RGY SOLUTIONS
Solar Panel Degradation: What to Expect Over 25 Years
Solar panels do not stop working the day their warranty ends. They simply produce a little less power each year, so slowly that most homeowners never notice month to month.
Solar panel degradation is a normal part of how the technology ages, not a sign that something has gone wrong. Understanding the pattern helps you know what a healthy system looks like at year 5 versus year 20. It also helps you spot when a drop in output actually needs a technician, rather than just time passing.
Here is what typically happens to a solar panel system across a 25 year lifespan. We will also cover what actually speeds up or slows down the process.
How Degradation Is Actually Measured
Manufacturers rate degradation as a percentage of output lost per year. Most quality panels sold in Australia today are rated at around 0.5 percent per year, sometimes less for premium brands.
That means a system producing 100 percent of its rated output in year one keeps most of that capacity long term. By year 25, it is typically still producing around 88 to 90 percent. It is a gradual slope, not a cliff edge.
Panel warranties reflect this. Most manufacturers guarantee a minimum output, often 80 to 87 percent, by year 25. Worth checking your specific solar panel warranty terms, since coverage varies between brands.
Years 1 to 5: Settling In
New panels actually perform close to, or occasionally slightly above, their rated output in the first year or two. After that, a small initial drop happens within the first six months. This is known as light induced degradation, usually in the range of 1 to 3 percent.
After this early dip, output settles into a steady, predictable decline. Most homeowners see almost no noticeable difference in their bills during this period. Dust, pollen and grime buildup on the panel surface will affect output far more than ageing does at this stage.
Years 5 to 10: Steady, Predictable Decline
This is the phase where degradation follows the manufacturer’s rated curve closely. A system losing 0.5 percent per year follows a simple curve. By year 10, it will be sitting at roughly 95 to 97 percent of its original output.
Inverters often need attention before panels do at this stage. Most inverters are rated to last 10 to 15 years, shorter than the 25 year panel lifespan. If your system’s output drops noticeably rather than gradually, get the inverter checked first. Do not assume the panels themselves are the problem. A technician can assess this through solar inverter repairs rather than a full panel replacement.
Years 10 to 15: Watch for External Factors
By this stage, the panels themselves are usually still performing close to expected levels. What changes more is everything around them. Roof sealant can wear and mounting brackets can loosen slightly. Years of Adelaide dust storms and bird activity also take their toll on panel surfaces.
Microcracks become more common in this window too. They often come from thermal expansion over repeated hot Adelaide summers, rather than any manufacturing fault. They are not always visible to the eye but can gradually reduce output. Our guide on solar panel microcracks explains how to spot the early signs.
Regular cleaning also matters more as a system ages. Built up grime blocks more light than it did when the panels were new and slightly more reflective. A professional solar panel cleaning service every year or two helps. It keeps output closer to what the panels are actually capable of.
Years 15 to 25: The Long Tail
Output continues its slow decline, but most well maintained systems are still generating meaningful power at this point. Take a 6.6kW system installed 20 years ago. Under the same conditions, it is likely producing somewhere between 5.8 and 6kW now, rather than the full 6.6kW.
This is also the stage where homeowners start weighing up their options. Keep the existing system running, or upgrade to newer, more efficient panels? Panel technology has improved substantially over the past two decades. A same sized upgrade can sometimes produce noticeably more power than the ageing system it replaces. If you are considering this step, a solar panel installation assessment can show whether an upgrade makes financial sense. This is especially worth checking with current rebate schemes in play. Our breakdown of the 2026 solar rebates covers what is currently available.
What Speeds Up Solar Panel Degradation
A few factors can push a system below its expected curve faster than normal:
- Extreme heat exposure, particularly on north facing roofs with poor ventilation underneath the panels
- Physical damage from hail, falling branches or foot traffic during other roof work
- Poor quality panels from budget installers using lower grade cells
- Infrequent cleaning, allowing dust and grime to bake onto the surface over summer
- Shading from growing trees that was not accounted for at installation
None of these are things you can fully prevent. Most can be managed, though, with regular maintenance and a proper initial installation.
Protecting Your Solar Investment
A yearly check up catches most issues well before they show up as a noticeable drop in your power bill. A solar service, safety check and clean covers the panels, wiring and inverter in one visit. It gives you a clear picture of how your system is actually performing against its expected curve.
If your bills have crept up and you are not sure why, do not just guess. It is worth getting a technician out to check whether it is genuine degradation or something else going on. Book an assessment through Easy Book and get a straight answer on how your system is tracking.
What This Means for You
Solar panel degradation is a slow, predictable process rather than something to worry about day to day. Understanding the curve helps you tell the difference between normal ageing and a genuine fault worth calling someone about.
If it has been a while since your system was checked, give the Sharpe team a call on 8262 5000. Or book a solar service online and get a clear picture of exactly how your panels are performing.
Frequently Asked Questions
Most quality panels degrade at around 0.5 percent per year, meaning a system typically retains 85 to 90 percent of its original output after 25 years.
No. Panels rarely stop producing power entirely. They simply continue to decline gradually beyond the warranty period. Many systems keep generating a useful amount of electricity well past year 25.
A sudden or sharp drop in output is usually not degradation. It typically points to a fault, dirty panels or an inverter issue rather than the panels ageing badly.
Yes. Dust, pollen and grime can block a meaningful amount of sunlight, especially over an Adelaide summer. Regular cleaning is one of the easiest ways to keep output closer to its rated potential.
Sometimes. If your panels are underperforming due to age or damage, an upgrade is worth considering. Newer technology could boost output enough that it pays for itself faster than expected, particularly with current rebates available.
