How do I troubleshoot common issues with home solar panel output?

Before You Begin: Safety and Baseline Checks

A sudden drop in your solar panel output is often caused by one of a few fixable issues. Before you climb onto your roof or open any electrical equipment, always prioritize safety. If you are uncomfortable working at heights or near electrical connections, stop and call a qualified solar installer. Also, check your system's monitoring app or inverter display first to confirm the output drop is real and not a software glitch. Note the time of day and weather conditions when the drop occurred.

Common No. 1: Shading and Debris

The most frequent cause of reduced output is partial shading. Even a small amount of shade from a new tree branch, a neighboring building, or a chimney can significantly reduce a panel's power, and in some systems, affect the entire string.

• What to check: Look for leaves, bird droppings, pollen, or snow accumulation on the panels. Check for new growth from nearby trees or shrubs that may have grown since the original installation.
• DIY fix: If panels are accessible and safe to reach, gently hose them off with a garden hose (use non-scaling water if possible) in the early morning or late evening. Never use abrasive sponges or pressure washers, as these can damage the glass and seals. For stubborn grime, a soft brush with a long handle and mild soapy water can work. Trim any overhanging branches yourself only if it is safe and allowed by local codes.

Common No. 2: Inverter or Monitoring Issues

The inverter is the brain of the system, converting DC power from panels to AC power for your home. If it shows a fault code or is not functioning, total output will drop to zero or near zero.

• What to check: Look at the inverter's display panel. What lights are on? Most inverters have a user manual that explains error codes. Common issues include a tripped breaker (on the inverter or your main panel), a loose connection, or a grid outage. If you have a string inverter, also check that each string of panels is connected properly inside the inverter.
• DIY fix: For a tripped breaker, flip it off, wait 30 seconds, and flip it back on. If the inverter shows a persistent error code, note the code and consult the manual. Do not open the inverter casing. If the inverter is flashing a warning light but no error code, a power-cycle (turning the inverter off and on via its switch) can sometimes reset minor glitches. If the issue returns, call a pro.

Common No. 3: Age-Related Degradation and Component Failure

All solar panels degrade over time, typically losing about 0.5% to 0.8% of their output per year according to industry studies. A sudden, sharp drop is not normal degradation.

• What to check: Compare current output to your system's historical performance from the same month and time of year. A gradual decline over several years is expected. A sudden 20% or more drop points to a specific problem like a failed bypass diode in a panel, a microinverter failure (in systems with individual microinverters on each panel), or a wiring issue.
• DIY fix: Look for visible damage on any panel, such as cracks, discoloration, or burn marks. If you have a system with microinverters, your monitoring software may tell you which specific panel is underperforming. There is no safe DIY repair for internal component failure. This requires a technician.

Common No. 4: Soiling and Weather Conditions

While rain helps, it does not fully clean panels. Dust, pollen, and air pollution can build up over weeks. Also, extremely hot weather can reduce panel efficiency, a phenomenon called temperature coefficient loss.

• What to check: Look for a consistent, thin layer of dust or grime across all panels. Note if your area has experienced extended dry periods. In very hot weather (above 85°F), expect a slight drop in efficiency. Snow can also block light, though panels are typically tilted to shed it.
• DIY fix: Light cleaning as described in No. 1. For temperature-related drops, there is no fix-it is a normal physical property. For snow, you can gently use a roof rake with a soft brush attachment to clear panels, but be careful not to damage the panel or roof shingles. Do not use hot water on cold glass.

When to Call a Pro

If you have tried the safe, basic troubleshooting steps above and output is still low, or if you see any of the following, call a licensed solar contractor:

• Persistent error codes on the inverter after a reset.
• Visible physical damage to any panel, wiring, or mounting hardware.
• Tripped breakers that immediately trip again after resetting.
• Monitoring completely offline and unresponsive.
• Any sign of arcing, burning smell, or smoke.

A professional can perform safety voltage tests, diagnose internal panel or string failures, and handle any warranty claims. Keep in mind that local electrical codes and climate conditions vary, so a local installer is your best resource for site-specific advice.