Degradation

What Is Degradation?

Degradation refers to the gradual, unavoidable power loss of solar modules over their lifetime. Modern modules lose approximately 0.3—0.5% of their rated power annually. After 25 years, they still typically deliver 85—90% of their original output.

Causes

• LID (Light Induced Degradation): Power loss in the first operating hours due to light exposure on the silicon (1—3%)
• LeTID (Light and elevated Temperature Induced Degradation): Degradation from light and elevated temperature, especially in PERC cells
• PID (Potential Induced Degradation): Degradation caused by high system voltage
• UV Degradation: Ageing of the encapsulant due to UV radiation
• Mechanical effects: Microcracks from wind, snow, or thermal cycling

Typical Progression

Period	Power Loss
First year (LID)	1—3%
Per year thereafter	0.3—0.5%
After 25 years	approx. 10—15% total
After 30 years	approx. 12—18% total

Practical Tip

Manufacturers typically guarantee at least 80% of rated power after 25 years. High-quality modules with glass-glass construction and TOPCon or HJT cells exhibit lower degradation rates. Degradation should be factored into yield planning.