Solar Panel Degradation: How Long Do Panels Last?
Solar panels degrade at 0.3-0.5% per year and last 25-30+ years. Learn about degradation rates, what causes them, and how to maximize panel lifespan.
How Long Do Solar Panels Last?
Solar panels are remarkably durable. Most panels are warranted for 25 years, but real-world data shows they continue producing electricity well beyond that. Studies of panels installed in the 1980s and 1990s show many still operating at 80 percent or more of their original capacity after 30 to 40 years.
The key factor determining panel longevity is degradation, the gradual loss of power output over time. Understanding degradation helps you plan your investment and set realistic long-term expectations.
What Is Solar Panel Degradation?
Degradation is the slow, natural decline in a solar panel's power output over time. All solar panels degrade, but the rate has improved dramatically with modern manufacturing techniques.
First-Year Degradation (LID)
New solar panels experience light-induced degradation (LID) during their first few weeks of sun exposure. Boron-oxygen complexes form in the silicon, temporarily reducing efficiency by 1 to 3 percent. This initial drop is a one-time event and is already factored into panel ratings and warranty terms.
Modern N-type panels (TOPCon, HJT) use phosphorus doping instead of boron, virtually eliminating LID. This is one of the many advantages of newer panel technologies.
Annual Degradation
After the initial LID period, panels degrade at a steady annual rate. The industry-standard assumption is 0.5 percent per year, but many modern panels perform significantly better:
At a degradation rate of 0.5 percent per year, a panel will produce roughly 87.5 percent of its original output at year 25. At 0.25 percent per year, it will still produce 93.75 percent.
What Causes Solar Panel Degradation?
Thermal Cycling
Daily temperature swings cause panels to expand and contract. Over thousands of cycles, this creates micro-stresses in solder joints and cell interconnections. Panels in climates with extreme temperature swings (hot days, cold nights) may degrade slightly faster than those in mild climates.
UV Exposure
Ironically, the sunlight that powers solar panels also slowly degrades the encapsulant materials that protect the cells. UV radiation causes yellowing or browning of the encapsulant (EVA or POE film), which reduces light transmission to the cells. Modern encapsulants are engineered to resist UV degradation far better than earlier materials.
Humidity and Moisture
Moisture intrusion can cause corrosion of cell metallization and delamination of encapsulant layers. Panels certified to IEC standards undergo rigorous damp-heat testing (85 degrees Celsius at 85 percent humidity for 1,000 hours) to verify moisture resistance. Quality panels from reputable manufacturers handle humidity well.
Potential-Induced Degradation (PID)
PID occurs when high system voltages cause ion migration within the panel, reducing cell performance. Modern panel designs and proper system grounding largely prevent PID. Anti-PID coatings and N-type cell technology have made this issue increasingly rare.
Mechanical Stress
Wind loads, snow loads, and hail impact create mechanical stress on panels. Modern panels are rated to withstand winds up to 140 mph and hailstones up to 1 inch in diameter at 50 mph. However, extreme events beyond these ratings can cause micro-cracking in cells, accelerating degradation.
Real-World Degradation Data
The National Renewable Energy Laboratory (NREL) analyzed degradation data from nearly 10,000 solar panel installations worldwide. Their findings:
How to Minimize Degradation
While you cannot prevent degradation entirely, you can take steps to ensure your panels last as long as possible:
Choose High-Quality Panels
Panels from reputable manufacturers undergo more rigorous quality control and use superior materials. Spending an extra $1,000 to $2,000 on premium panels can mean 5 to 10 percent more energy production over the system's life due to lower degradation rates.
Ensure Proper Installation
Correct mounting, wiring, and grounding prevent issues like PID and excessive mechanical stress. Choose an experienced, certified installer who follows manufacturer guidelines precisely.
Keep Panels Clean
While rain does most of the cleaning, periodic removal of heavy dirt, bird droppings, or pollen buildup ensures maximum light reaches the cells. In dusty environments, annual cleaning can maintain an extra 2 to 5 percent of production.
Monitor Your System
Use your monitoring system to track production over time. A sudden drop in output may indicate a panel issue that is fixable under warranty rather than normal degradation.
Trim Nearby Trees
Shade from growing trees reduces production and can cause hot spots on partially shaded cells, accelerating localized degradation. Keep vegetation trimmed back from your panel array.
When to Replace vs. Ride It Out
At year 25, a well-maintained solar panel is still producing 85 to 90 percent of its original output. That is still a lot of free electricity. Unless the panels are physically damaged or producing significantly below warranty levels, there is rarely a financial reason to replace them.
Many homeowners will find that their panels are still going strong at year 30 or beyond, even after the warranty expires. The electronics (inverters, particularly string inverters) are more likely to need replacement before the panels themselves.
What Happens at End of Life?
When panels do eventually reach end of life, they can be recycled. Solar panel recycling recovers valuable materials including silicon, silver, copper, and aluminum. Recycling infrastructure is still developing, but several companies now offer panel recycling services, and regulations requiring recycling are emerging in various states and countries.
The Bottom Line
Solar panels are one of the most durable consumer products available, lasting 25 to 30 years or more with minimal maintenance and gradual degradation. Modern panels degrade slower than ever, and premium brands like SunPower, REC, and Panasonic offer industry-leading longevity.
When you get quotes through SmartEnergyUSA, pay attention to the degradation rate and performance warranty of each panel option. A small difference in annual degradation translates to thousands of dollars in additional energy production over the system's life.
