Why might my home solar panels be underperforming?

Why might my home solar panels be underperforming?

Solar panels are a significant investment, and seeing lower energy production than expected can be concerning. Before assuming a major failure, understand that performance dips often stem from manageable factors. This article outlines common causes of underperformance and offers practical troubleshooting steps.

Common Causes of Reduced Solar Output

Shading and Obstructions

Even partial shading from a tree, chimney, or new building can dramatically reduce a panel string's output. Panels in a series are only as strong as the least-productive panel. Check for overgrown vegetation, dirt, bird droppings, or seasonal shadows that may have changed since installation.

Dirt and Debris Accumulation

Dust, pollen, leaves, and bird droppings block sunlight. In dry or dusty climates, a layer of grime can reduce efficiency by 5-10% or more. Rain alone may not fully clean panels, especially if they are at a low tilt angle.

Inverter or Monitoring Issues

The inverter converts DC power from panels to usable AC. A faulty inverter can stop production entirely. Check your monitoring system for error codes or unusually low output. Some inverters have physical LED indicators to help diagnose problems.

Temperature and Weather

Solar panels lose efficiency as temperatures rise above 77°F (25°C). On hot days, expect a modest drop. Conversely, very overcast or rainy periods naturally reduce output. These are normal, not defects.

System Age and Degradation

All panels degrade slowly over time, typically losing 0.5% to 1% efficiency per year. If your system is older than 10 years, gradual decline is expected. However, sudden sharp drops indicate a problem.

How to Troubleshoot

Start with visual inspection

Look for obvious debris, cracks, or damage. Check that no new construction or trees have created shading. Do not walk on panels; use binoculars or a drone from a safe distance.

Check your monitoring system

Review daily and monthly production graphs. Compare to historical data for the same season. A single low day might be weather; a week of low output points to a real issue.

Clean panels (safely)

If dirt is the culprit, clean during early morning or late evening using a soft brush or squeegee and deionized water. Never use abrasive tools or high-pressure sprayers, which can damage seals.

Verify inverter operation

Look at the inverter display or app. If it shows a fault code, consult the manual. Many inverters have a reset procedure. If the inverter appears dead, call a professional.

When to Call a Professional

Persistent underperformance

If you have cleaned panels, checked for shade, and ruled out weather, but output remains low, contact your installer or a licensed solar contractor.

Electrical issues

If you notice tripped breakers, burn marks, or unusual sounds from the inverter, shut down the system and call a pro immediately. Do not attempt electrical repairs yourself.

Warranty concerns

Many solar panels and inverters come with 25-year warranties. Unauthorized repairs can void coverage. Always check warranty terms before working on components.

System design or component failure

Problems like a failed microinverter, damaged wiring, or a faulty panel often require specialized diagnostic tools. A technician can use infrared cameras or IV curve testing to pinpoint issues.

Final Thoughts

Underperforming solar panels are rarely a sign of total system failure. Start with simple checks like shade, dirt, and monitoring data. Regular maintenance and prompt attention to warning signs help keep your system running efficiently for years. Remember that local conditions, such as climate and utility interconnection rules, can affect performance. When in doubt, consult a qualified solar professional.