Solar Panel Degradation in 2026: What 20 Years of Real Data Shows

When someone asks me whether solar panels "wear out," I like to point them to a small set of arrays installed in the late 1990s and early 2000s that are still clipping along in the field. Two decades in, the best of them are producing 88–92% of their original rated output. That is not a marketing promise. That is a read off the inverter screen.

Degradation is the slow, steady loss of power output that happens to every solar panel over time. In 2026, it is one of the most misunderstood parts of home solar — partly because the number is small, partly because it gets confused with catastrophic failures, and partly because warranties are written in a way that makes the whole thing sound scarier than it is.

Here is what the data actually says, how to read a modern warranty, and how the numbers plug into your payback math.

How Much Do Solar Panels Really Degrade Each Year?

The clearest answer comes from the National Renewable Energy Laboratory's ongoing review of fielded modules. NREL's widely cited meta-analysis of nearly 2,000 degradation measurements found a median loss of about 0.5% per year for crystalline silicon panels, with newer (post-2000) installations clustering closer to 0.4%.¹

Put into plain English: if your 10 kW system produces 14,500 kWh in its first year, you should expect roughly 14,427 kWh in year two and somewhere around 13,140 kWh in year 20. You do not wake up one morning to a dead array. You wake up to an array that is a couple of percent quieter than it was five years ago.

The 2025 International Technology Roadmap for Photovoltaics — an industry consensus document — reported that top-tier monocrystalline PERC and TOPCon panels now advertise 0.25–0.4% annual degradation with a first-year "light-induced" drop of about 1–2%. N-type TOPCon and heterojunction (HJT) modules — the kind showing up on most 2026 residential quotes — tend to sit at the low end of that range.²

A few patterns show up consistently in the field data:

Degradation is not linear. Most panels lose 1–2% in their first year as light-induced degradation stabilizes, then settle into a much slower annual slope. That is why warranties talk about "year one" separately from "years 2–25."

Hotter climates degrade panels faster. Arrays in Phoenix, Las Vegas, and South Texas degrade faster than arrays in Minnesota or Oregon because degradation is partly a temperature-driven chemistry problem. The difference is small — typically 0.1–0.2 percentage points per year — but it compounds.

Thin-film and older polycrystalline panels degrade faster than modern mono PERC/TOPCon. If you are looking at a used or 10-year-old system as part of a home purchase, assume a higher degradation rate and ask for production data.

What the Warranty Actually Promises

Here is where homeowners get tripped up. Solar panel warranties have two pieces, and they mean very different things.

Product warranty. This covers manufacturing defects — delamination, broken busbars, corroded connectors. In 2026, the mainstream product warranty has moved from 12 years to 25 years at most Tier 1 brands (Qcells Q.TRON, REC Alpha Pure-RX, Silfab Elite, Canadian Solar HiKu7, Jinko Tiger Neo, Maxeon 7). A few premium brands — Maxeon, REC — now advertise 40-year product warranties. If the panel itself breaks for a manufacturing reason inside this window, the manufacturer is supposed to replace it.

Performance (linear power) warranty. This guarantees a minimum output curve. The 2026 standard for Tier 1 mono panels looks like this: at least 98% of rated power at the end of year one, then no more than 0.4% decline per year, ending at roughly 88–89% of nameplate in year 25. Maxeon 7 and REC Alpha Pure-RX are currently guaranteeing 92% at year 25, which implies roughly 0.25% annual degradation.

If your system drops below the warrantied curve and you can prove it with production data, the manufacturer owes you a remedy (usually replacement panels or a cash-equivalent credit). The proof part is important. Keep your monitoring turned on.

What warranties do not cover:

Normal soiling (dust, pollen, bird droppings). Squirrel damage. Hail above the tested impact level (most panels are certified for 1" hail at 50 mph; some — like Solaria PowerXT-R — are tested for larger). Microinverter or string inverter failures (those are warrantied separately — usually 10–25 years).

How Degradation Actually Affects Your Payback

When you run the numbers on a home solar system, degradation is baked into the 25-year production estimate. A reputable solar quote should show you year-by-year production with a 0.4–0.5% annual haircut and a 1–2% first-year drop. If you do not see degradation modeled, ask. (Our solar calculator models a 0.5% annual degradation rate by default.)

A rough example for a 10 kW system in a moderate climate with a $3.20/W installed cost, no federal tax credit (Section 25D expired at the end of 2025), and a local utility rate of $0.17/kWh escalating 3% per year:

Year 1 production: ~14,500 kWh, offsetting roughly $2,465 of electricity. Year 10 production: ~13,870 kWh, offsetting ~$3,050 (higher dollar value because of rate escalation). Year 25 production: ~12,950 kWh, offsetting ~$4,420. Cumulative 25-year offset: roughly $78,000. Payback window: 11–13 years for cash buyers; longer for loans depending on APR.

Note that rate escalation tends to outrun degradation. Your system produces slightly less each year, but each kWh is worth more, which is why long-run solar math still pencils out in most of the country even without the 30% federal credit.

What You Can Actually Do About Degradation

You cannot stop the chemistry. You can stop losing extra output to things that look like degradation but are not.

Keep the array washed. A dusty array in the Southwest can look 5–8% "degraded" when it is really just dirty. A rinse twice a year — or opt-in cleaning via your installer — usually restores output.

Trim vegetation. New tree growth that shades even one cell of one panel can drop that whole string's output. If your production report is diving every September, look up.

Check monitoring quarterly. The whole point of SolarEdge, Enphase, Tesla, or Generac monitoring apps is to catch a failing module or microinverter before the warranty window closes. Twenty minutes, four times a year.

Keep your commissioning report. If you ever need to file a performance claim, the original baseline matters. Save the PDF your installer gave you at handoff.

The 2026 Bottom Line

Degradation is real but small. A quality 2026 residential array will produce 88–92% of its nameplate power a quarter century after it went live. The bigger risks to your long-term output are inverter failures (inverters usually get replaced once during the panel's life), squirrel and hail damage, and people who forget to look at the monitoring app.

If you are getting quotes, ask each installer for three things: the panel brand's current linear performance warranty curve, the degradation assumption used in their 25-year production estimate, and the inverter warranty length. Compare those three numbers, not just the sticker price.

And if you are shopping in a state with strong net metering or SRECs — New Jersey, Massachusetts, Illinois, California NEM 3.0 — a modest difference in degradation can change your 25-year cash flow by a few thousand dollars. Worth an hour of homework.

Ready to run the numbers on your own roof? Start with our free solar savings calculator and check your state's current rules in the incentive search. If you already have quotes and want a second opinion on production assumptions, our FAQ walks through the math line by line.

Sources

Footnotes

1. Jordan, D.C., Kurtz, S.R., VanSant, K., Newmiller, J. "Compendium of photovoltaic degradation rates." National Renewable Energy Laboratory. https://www.nrel.gov/docs/fy16osti/65040.pdf ↩

2. International Technology Roadmap for Photovoltaics (ITRPV), 2025 Results. VDMA. https://www.vdma.org/international-technology-roadmap-photovoltaic ↩