Solar Panel Degradation — How Much Power Do Panels Lose Over Time?

What Is Solar Panel Degradation?

All solar panels gradually lose power output over their lifetime through a natural process called degradation. This occurs due to UV exposure, thermal cycling, moisture ingress, and internal cell defects. Understanding degradation rates is critical for estimating long-term energy yield and financial returns.

Types of Degradation

1. Light-Induced Degradation (LID)

Occurs in the first hours of sun exposure. P-type PERC cells lose 1–3% from boron-oxygen defects. N-type cells (LONGi Hi-MO 7) are virtually immune, losing less than 0.5%.

2. Potential-Induced Degradation (PID)

Caused by high voltage and humidity. P-type cells require anti-PID treatment. N-type cells have inherent PID resistance.

3. Annual Degradation

Slow, continuous power loss from UV damage, encapsulant yellowing, and cell micro-defects.

Degradation Rates by Technology

Technology	First-Year Loss	Annual Rate	Output at Year 25	LONGi Product
Polycrystalline	3.0%	0.70%/year	~80%	N/A
Mono PERC (P-type)	2.0%	0.55%/year	~84.8%	Hi-MO 6
N-type TOPCon	1.0%	0.40%/year	~89.4%	Hi-MO 7
HJT	1.0%	0.40%/year	~89.4%	N/A

Why N-type Panels Degrade Less

• No B-O defects: Phosphorus doping eliminates boron-oxygen LID
• Better passivation: TOPCon's tunnel oxide layer protects the cell surface
• Higher-quality wafers: N-type silicon has fewer defects and higher purity
• PID immunity: Eliminates a major source of field degradation

Financial Impact of Degradation

For a 20 kW system over 25 years in Dubai:

• Mono PERC (0.55%/year): Cumulative energy = 691,000 kWh
• N-type TOPCon (0.40%/year): Cumulative energy = 713,000 kWh
• Difference: 22,000 kWh more from N-type = ~AED 9,900 additional value over 25 years

How to Minimise Degradation

• Choose N-type panels (LONGi Hi-MO 7) with lowest degradation rates
• Ensure proper ventilation to reduce thermal stress
• Avoid micro-cracking during installation — handle panels carefully
• Use quality mounting systems that minimise mechanical stress
• Monitor system output to detect abnormal degradation early

Frequently Asked Questions

How much do solar panels degrade per year?

N-type TOPCon panels like LONGi Hi-MO 7 degrade at 0.40%/year. Mono PERC degrades at 0.55%/year. Polycrystalline degrades at 0.70%/year.

Do solar panels last 25 years?

Yes. Premium panels like LONGi Hi-MO 7 are warrantied for 30 years and will continue producing beyond that, though at reduced output. After 25 years, expect approximately 89% of original output for N-type panels.

Can degradation be reversed?

No. Degradation is a permanent, irreversible process. However, choosing panels with low degradation rates (N-type) minimises lifetime losses.