Solar Panel Degradation & Long-Term Performance: What It Means for You

Investing in solar energy is a long-term decision—one that’s expected to deliver value, savings, and reliability for decades. But over time, even the most efficient solar panels gradually lose some of their original output. This slow decline, known as solar panel degradation, is a natural part of solar system aging and something every homeowner should understand.

Here’s what degradation means, what causes it, and how it affects long-term performance.

What Is Solar Panel Degradation?

Solar panel degradation refers to the slow reduction in the amount of electricity a solar panel can generate as it ages. This process is expected and occurs gradually over time due to exposure to sunlight, heat cycles, and environmental conditions.

Importantly, degradation doesn’t mean failure. Even after 25 years, well-installed systems can continue to produce meaningful energy output.

How Quickly Do Panels Degrade?

Most panels degrade at an average rate of 0.3% to 0.8% per year, depending on the brand, material quality, and local climate. After 25 years of use, a typical solar panel will operate at around 80% to 90% of its original capacity.

For example:
– A solar system that generates 10,000 kWh in year one may still produce between 8,000 and 9,000 kWh annually by year 25.
– Premium brands often offer lower degradation rates, meaning better long-term performance and more value over time.

What Causes Degradation?

Several environmental and mechanical factors contribute to solar panel degradation. These include: UV exposure (long-term sunlight exposure gradually affects panel materials), thermal cycling (daily expansion and contraction caused by temperature shifts), and moisture exposure (humidity or water intrusion can degrade internal components). Other factors such as mechanical stress (including wind, debris impact, or improper installation) can significantly impact degradation.

It’s important to note that most degradation is minor and manageable: especially when using high-quality panels installed by experienced professionals!

How Performance Warranties Address This

Solar panels typically come with two warranties: a product warranty (covering defects) and a performance warranty (guaranteeing output levels over time).

The performance warranty is especially relevant here. It ensures that your panels will continue producing a certain percentage of their original output for 20 to 25 years. Standard performance warranties often promise:
– 90% output at year 10
– 80% output at year 25

This coverage gives homeowners confidence that their system will remain productive even as output gradually declines.

Does Degradation Make Solar Less Effective?

Not at all. Degradation is expected and already factored into most solar savings projections. Even with a small annual decrease in performance, homeowners continue to see strong returns on their investment—especially in California, where energy rates are high and solar exposure is ideal.

Most systems still generate the majority of their initial output well beyond the 25-year mark.

Tips for Maximizing Long-Term Performance

Although you can’t prevent degradation entirely, you can take steps to reduce its impact:
– Choose Tier 1 solar panels (these are more durable and have lower degradation rates)
– Keep panels clean and clear of dust or debris
– Trim nearby trees to avoid shading over time
– Monitor your system regularly using the provided app
– Schedule periodic inspections to catch any issues early

A well-maintained system will not only perform more efficiently—it may also last longer than the warranty suggests.

Reliable Energy for Decades

Solar panel degradation is a normal part of a system’s lifespan. It doesn’t mean you’ll lose your energy savings or need to replace your panels any time soon. With proper planning, quality equipment, and ongoing care, your solar system can continue delivering reliable power and financial value for years to come.

Have questions about panel performance or your system’s expected output? Contact Plug It In Solar to speak with a solar expert.