Solar panels are one of the few home upgrades sold on a 25-year promise, so it is fair to ask what actually happens to them over that quarter century. The honest answer is that they slowly make a little less power each year, a process called degradation, but the decline is gentle, predictable, and far smaller than most buyers fear. A panel does not fall off a cliff at year 20; it eases down a shallow slope and keeps working long after. This guide covers the real solar panel degradation rate, the annual degradation of solar panels in plain numbers, what the performance warranty guarantees, and how a careful estimate already bakes the decline in.
What Solar Panel Degradation Actually Means
Degradation is the slow, permanent loss of a panel’s power output as it ages. It is not a malfunction and not a sign of a bad panel. It is the normal, expected wear of a semiconductor device that spends decades in the sun.
| Concept | What It Is | Permanent? |
|---|---|---|
| Degradation | Gradual, year-over-year decline in maximum output | Yes, cumulative and permanent |
| Temporary output dip | A cloudy day, heat, or a dusty panel | No, fully recovers |
Understanding how a solar panel actually produces power makes clear why degradation happens: the cell is doing real physical work every daylight hour, and no material does that forever without a trace of wear. Those short-term swings connect instead to how panel efficiency shapes your estimate, not to long-term aging.
The Solar Module Degradation Rate, in Real Numbers
The degradation rate is simply the percentage of output a panel loses per year. It comes in two parts: a small settling drop in the first year, then a steady, slower slope for the rest of the panel’s life.
| Phase | Typical Range | When It Happens |
|---|---|---|
| First-year settling drop (light-induced degradation) | 1% to 3%, one time only | During the first few months in the sun |
| Annual degradation, standard panels | About 0.5% per year | Every year after year one |
| Annual degradation, premium panels | About 0.25% to 0.3% per year | Every year after year one |
Reputable manufacturers already factor the first-year settling into their published numbers, so the panel you buy is rated with this initial dip in mind rather than surprising you with it later. That difference between 0.5% and 0.25% per year sounds tiny, but compounded over decades it adds up, which is one reason panel quality is worth weighing alongside price when you compare the different types of solar panels.
How Much Power Panels Lose Over 25 Years
Put the two pieces together, and the 25-year picture becomes easy to sketch.
| Year | Standard Panel (0.5%/yr) | Premium Panel (0.25%/yr) |
|---|---|---|
| 1 | 97% | 97% |
| 5 | 95% | 96% |
| 10 | 92.5% | 94.5% |
| 15 | 90% | 93% |
| 20 | 87.5% | 91.5% |
| 25 | 85% | 90% |
For a mainstream panel losing about 0.5% a year after the first year, roughly 85 to 88% of the original output typically remains at year 25. Premium panels with a shallower slope often hold 90% or more. In plain terms, a system rated to cover most of your electric bill on day one still covers the large majority of it decades later.
Why 25 Years Is Not the Finish Line
The 25-year mark is a warranty milestone, not an expiration date. Panels do not stop working when the warranty ends; they simply keep declining at the same gentle pace while still producing meaningful power for years beyond. In practice, the panels often outlast other parts of the system, which is why it is smart to think about your roof’s age and condition before installation.
What a Slower Degradation Rate Is Actually Worth
A lower annual rate is not just a spec sheet number; it translates directly into more usable electricity over the system’s life.
| Scenario | Cumulative Output Lost by Year 25 (Illustrative, 6 kW System) |
|---|---|
| Premium panel, 0.25%/yr | Lowest lifetime loss |
| Standard panel, 0.5%/yr | Roughly double the lifetime loss of the premium panel |
| Budget panel, 0.75%/yr or higher | Roughly triple the lifetime loss of the premium panel |
The exact dollar impact depends on your system size and utility rate, but the pattern holds everywhere: every fraction of a percentage point in annual degradation compounds over 25 years, and it is one more reason panel quality deserves attention alongside sticker price when comparing bids.
The Performance Warranty That Puts It in Writing
The reassuring part of degradation is that you do not have to take a manufacturer’s word for it. The rate is guaranteed in writing through a dedicated warranty, separate from the ones covering defects and labor.
| Panel Grade | Typical Guaranteed Output at Year 25 |
|---|---|
| Standard | Around 84% to 85% |
| Premium | Around 90% to 92% or higher |
Every quality panel carries a performance warranty, sometimes called a power-output or production warranty, that promises the panel will still produce at least a stated percentage of its original rating at year 25. If a panel degrades faster than the curve the warranty promises, the manufacturer is on the hook. This is distinct from the equipment and workmanship coverage, and it is worth understanding how the separate warranties on your solar system fit together before you sign.
Reading the Degradation Curve on a Quote
A good proposal will spell out both the first-year figure and the annual rate, along with the guaranteed year-25 percentage.
- Ask for the exact first-year and annual degradation figures in writing, not just a general “25-year warranty” claim.
- Compare the guaranteed year-25 output floor across bids, not just the sticker price.
- Line up more than one solar quote side by side, since two proposals that look identical on headline price can differ meaningfully in the fine print.
What Makes Panels Degrade Faster or Slower
Degradation is not a fixed fact for every panel in every location. The published rate assumes reasonable conditions, and both the environment and the hardware can nudge the real-world pace up or down.
- Sustained heat. The biggest accelerator of long-term aging, separate from the temporary output dip heat causes on a given afternoon. See how weather affects solar panels for the short-term side of that picture.
- Installation quality. A proper air gap under the panels and quality mounting help them run cooler and age more slowly. Sloppy installation that traps heat or lets moisture intrude can push degradation past the expected curve.
- Panel technology and build quality. Higher-grade cells, better encapsulants that resist moisture, and sturdier construction all slow the aging process. This is what a premium panel buys you over 25 years: not just a higher starting efficiency but a slower decline from it.
How Degradation Shapes Your Estimate and Savings
Because degradation is predictable, it belongs in any honest projection of what a system will produce and save. A credible estimate treats it as a known input, not a surprise.
A careful proposal models production across the full life of the system, applying the expected degradation curve year by year rather than assuming the panels make their day-one output forever. That kind of full solar design bakes degradation in from the start, and it is part of what goes into everything that determines your solar estimate. If an estimate seems to assume the panels never slow down, treat that as a red flag.
Modest degradation does not undo the economics of solar, but it does mean the biggest savings come in the early years when output is highest. Because solar still saves money over the long run even after accounting for the decline, the gentle slope simply shifts a bit more value toward the front of the timeline. It matters even more now that NEM 3.0 changes how every kilowatt-hour is valued, since a panel that holds its output well protects the export and self-consumption value the estimate counted on.
Built to Last the Distance
Solar panel degradation is one of the quietest facts about owning a system. Panels lose a small percentage in their first year, then decline at roughly half a percent annually, leaving the typical module producing around 85 to 90% of its original output after 25 years and still going beyond that. A performance warranty puts that curve in writing, panel quality decides how shallow the slope is, and a good estimate bakes the whole thing in from the start. If you want to see how the expected degradation curve factors into real production and savings numbers for your home, you can begin with a free, no-pressure solar estimate from Axia.
Frequently Asked Questions
What is a good solar panel degradation rate?
A solid modern panel loses about 0.5% of its output per year after a small first-year settling drop. Premium panels do better, often around 0.25% to 0.3% annually. The lower the annual rate and the higher the guaranteed year-25 output floor, the more total energy the panel delivers over its life.
What is the annual degradation of solar panels?
Most modern panels lose roughly 0.5% of their output each year after an initial first-year settling drop of 1% to 3%. Premium panels degrade more slowly, often around 0.25% to 0.3% per year. This rate is guaranteed in writing through the manufacturer’s performance warranty.
What is a typical solar module degradation rate?
Industry data places typical modern solar modules at about 0.5% lost per year after the first year, with premium modules often performing closer to 0.25% to 0.3% annually. Manufacturers publish this as part of the performance warranty, which also guarantees a minimum output percentage at year 25.
How much power do solar panels lose over 25 years?
For a typical panel degrading around 0.5% a year, roughly 85 to 88% of the original output usually remains at year 25. Premium panels often hold 90% or more. The loss is real but gradual, so a system sized to cover most of your bill on day one still covers the large majority of it decades later.
Do solar panels stop working after 25 years?
No. The 25-year mark is a warranty milestone, not an expiration date. Panels keep producing power well beyond it, continuing to decline at the same slow pace. In many cases, the panels outlast other parts of the system, such as the roof beneath them or the inverter.
What is light-induced degradation?
Light-induced degradation is a one-time break-in loss that happens during a panel’s first months in the sun, typically in the range of 1% to 3%, as the cell chemistry stabilizes. It occurs once and does not repeat, and reputable manufacturers already account for it in their published ratings.
Does the warranty cover degradation?
Yes. A dedicated performance or power-output warranty guarantees the panel will still produce at least a stated percentage of its original rating at year 25, commonly 84% to 92% depending on panel grade. If a panel degrades faster than that promised curve, the manufacturer is responsible. This coverage is separate from the equipment-defect and workmanship warranties on the system.