Solar Panel Degradation Rate: NREL Data & Climate Impact (2026)

Solar panel degradation rate runs a median of 0.5% per year (NREL, 2023), but premium cells roughly halve that and hot or humid climates speed it up. This data deep dive from Hongyu ‘s engineering team breaks down degradation by cell technology, climate multipliers, and how to tell normal aging from a warranty-worthy fault.

Key Takeaways

Median solar panel degradation is 0.5% per year for modules manufactured after 2010 (NREL 2023, 50,000 modules tracked).

Premium TOPCon and HJT cells degrade at 0.25 to 0.35% per year. PERC monocrystalline at 0.5 to 0.55%. Polycrystalline at 0.6 to 0.8%.

First-year degradation is higher than steady-state: typically 1.5 to 2.5% on day-1 to year-1, then linear thereafter.

Climate matters: arid hot adds 0.1 to 0.2%/year. Humid hot adds 0.2 to 0.3%/year. Coastal salt adds 0.1 to 0.3%/year.

Abnormal triggers warranty action: single-panel drop greater than 20% versus siblings, or whole-system year-over-year drop greater than 10% under same weather.

What is solar panel degradation?

Solar panel degradation is the gradual loss of output capacity over time. A new panel rated at 400W produces less than 400W in year 5, less still in year 10, and so on.

Two distinct phases:

Light-induced degradation (LID): 1.5 to 2.5% drop from day-1 nameplate over the first 12 months. This is built into Tier-1 power warranties.
Annual linear degradation: 0.25 to 0.8% per year after year 1, depending on cell technology, climate, and maintenance.

The warranty floor for any Tier-1 module is 84.8% of original output at year 25.

The NREL 2023 degradation benchmark

The 2023 PV Module Reliability Benchmark is the most-cited research on real-world degradation. NREL tracks roughly 50,000 installed modules across US climate zones.

Key findings for modules manufactured after 2010:

Statistic	Value
Median annual degradation	0.5%/year
Top quartile (best 25%)	<0.4%/year
Bottom quartile (worst 25%)	>0.65%/year
Pre-2010 modules (legacy)	0.7–1.0%/year
Manufacturing improvement since 2010	~30% reduction in degradation rate

The improvement curve reflects two things: better cell technology (PERC, TOPCon, HJT) and tighter manufacturing tolerances at Tier-1 solar panel brand (including Hongyu).

35-year output projection

The chart below applies the NREL median (0.5%/year) and top-quartile (0.4%/year) rates to a new Tier-1 module rated at 100% on day one.

Source: NREL PV Module Reliability Benchmark, 2023.

Solar panel degradation rate by cell technology

Solar cell technology is the largest single factor in degradation rate.

Cell technology	Year-1 LID	Annual rate	Year-25 output
HJT (Heterojunction)	1.0–1.5%	0.25–0.35%	91–94%
TOPCon (N-type)	1.5–2.0%	0.30–0.40%	89–92%
PERC monocrystalline	2.0–2.5%	0.50–0.55%	84–87%
Polycrystalline (legacy)	2.5–3.0%	0.60–0.80%	76–82%
Thin-film CdTe (First Solar)	1.5–2.0%	0.50–1.00%	73–84%
Amorphous silicon (a-Si) (legacy thin-film)	10–25%	1.0–1.5%	50–65%

A premium HJT panel can produce 8 to 10% more power at year 25 than a budget PERC panel of the same nameplate rating. Across a 25-year ownership period, that gap exceeds the price difference between premium and budget modules.

For deeper brand-by-brand comparison, see best solar panel brands 2026.

How climate affects solar panel degradation

Climate stacks on top of base degradation rate. The same module degrades faster in some US regions.

Climate zone	Degradation multiplier	Net annual rate (PERC baseline 0.5%)
Temperate (Mid-Atlantic, Pacific Northwest)	1.0×	0.50%
Arid hot (Southwest, Mountain West)	1.2–1.4×	0.60–0.70%
Humid hot (Florida, Gulf Coast)	1.4–1.6×	0.70–0.80%
Coastal (within 5 mi of ocean, no salt-rated hardware)	1.2–1.6×	0.60–0.80%
Cold (Mountain West, Northern Plains)	0.9–1.0×	0.45–0.50%
High-altitude (above 8,000 ft)	1.1–1.3×	0.55–0.65% (UV exposure)

The mechanisms differ: arid hot is thermal cycling stress, humid hot is encapsulant moisture ingress, coastal is salt corrosion, and high-altitude is UV-induced anti-reflective coating wear.

How to diagnose abnormal solar panel degradation

Normal degradation is invisible day-to-day. Abnormal degradation shows up in your monitoring app or visual inspection.

Single-panel abnormalities

Open per-panel monitoring data in your inverter app. Flag any panel making 20% or more less than its siblings under the same conditions:

Year 0–2: Manufacturing defect; file warranty claim immediately
Year 3–10: Likely impact damage (hail, debris) or hot spot; file warranty claim if no impact event documented
Year 10–25: Likely cell-level encapsulant degradation; covered under most product warranties (12-year minimum)
Year 25+: Out of warranty; replacement decision per how long do solar panels last

Whole-system abnormalities

Compare year-over-year output by month under similar weather. A drop greater than 10% with no shading change is abnormal.

Common causes:

Symptom	Likely cause	Action
Sudden 15%+ drop, no weather change	Inverter fault	Schedule pro inspection
Gradual 3–5% per year drop	Soiling buildup	Clean and re-measure
Sudden 20%+ drop, one quadrant	Wiring fault or rodent damage	Service call
Slow 1.5–2%/year over 3+ years	Climate-accelerated degradation	Re-rate expectations, no action needed

Diagnostic tree: solar panel wiring issues.

What does the warranty actually cover?

Tier-1 manufacturers (Hongyu , REC, Jinko, Q CELLS, LONGi, Canadian Solar, SunPower) all offer linear power warranties with these standard terms:

Year 1 floor: 97% of nameplate
Year 25 floor: 84.8% of nameplate
Linear interpolation between years

If your panel falls below the warranty curve and you have documented annual inspections (see annual maintenance checklist), the manufacturer replaces it at no cost. Documentation matters: claims without inspection records are denied at higher rates.

Frequently Asked Questions

What is a good degradation rate for solar panels?

Below 0.5% per year is good. Below 0.35% per year is exceptional (premium HJT or TOPCon panels including Hongyu solar panels). Above 0.65% per year is below industry standard.

How fast do solar panels lose efficiency?

Median rate is 0.5% per year per NREL 2023 data. First-year drop is higher (1.5 to 2.5%) due to light-induced degradation, then linear thereafter.

Why do solar panels degrade?

Three primary mechanisms: light-induced degradation in the first year (UV breaks down boron-oxygen bonds in p-type silicon), thermal cycling stress in years 1+, and encapsulant moisture ingress over decades.

What is the difference between LID and annual degradation?

LID (light-induced degradation) is a one-time 1.5 to 2.5% drop in the first year. Annual degradation is the steady 0.25 to 0.8% per year loss thereafter.

Do solar panels degrade faster in hot climates?

Yes. Arid hot climates add 0.1 to 0.2% per year. Humid hot adds 0.2 to 0.3% per year. Coastal salt without salt-rated hardware adds 0.1 to 0.3% per year.

How can I slow solar panel degradation?

Five practices help: clean 2 to 4 times per year, run the annual maintenance checklist, prevent shading, update inverter firmware annually, and choose Tier-1 PV modules with HJT or TOPCon cells.

How do I know if my solar panel is degrading too fast?

Compare per-panel monitoring data across siblings. A single panel making 20% or more less than neighbors is abnormal. A whole-system year-over-year drop greater than 10% under same weather is abnormal.

Does solar panel degradation invalidate the warranty?

No. Linear power warranties cover degradation up to the published curve. They invalidate if cleaning damages void coverage (pressure washing, walking on glass) or if scheduled inspections are skipped.

Sources and references

NREL (2023). PV Module Reliability Benchmark.
IEC (2021). IEC 61215: Terrestrial PV modules – design qualification. https://webstore.iec.ch/en/publication/61345.
UL (2017). UL 61730: PV module safety qualification. R

Related guides

Disclosures: Degradation data reflects NREL 2023 and Hongyu field performance through May 2026. Editorial reviewed by the Hongyu Solar engineering team.

By Peter: Peter is a Senior PV & Energy Storage Engineer at Hongyu Supply Chain. As a seasoned expert in the renewable energy industry, he focuses on solar power generation, smart energy storage systems, and clean energy supply chains, delivering valuable technical analysis and industry trend insights to global audiences.