Quick Answer
Okay, so your monitoring app is flagging one panel as underperforming, right? Often, this points to a failed bypass diode. This small component is designed to shunt current around shaded or damaged cells, preventing the entire panel's output from dropping to zero. When it fails, the affected cells can't be bypassed, leading to a significant power drop from that panel, and sometimes even localized discoloration or 'hot spots.' Fixing it typically requires getting on the roof. While the diode itself is inexpensive, the repair involves safely accessing the panel, often disassembling its junction box, and performing delicate soldering. This type of repair is best left to a qualified solar technician due to safety risks and the potential to void panel warranties. Expect to pay a few hundred dollars for a service call and the repair.
Common Symptoms
Possible Causes
Step-by-Step Diagnosis
Step 1
Open your solar monitoring app (Enphase, SolarEdge, etc.). Compare the daily kWh production of the suspect panel to the panels directly next to it. Look for a consistent, significant difference.
Step 2
If you can do so safely from the ground or a window, visually inspect the panel. Look for any obvious signs of damage, burn marks, or debris causing shade.
Step 3
(Pro Step) Use a thermal imaging camera to look for 'hot spots.' A failed diode will cause a cell or group of cells to glow significantly hotter than the rest of the panel.
Step 4
(Pro Step - Danger!) After a full system shutdown, a technician will open the panel's junction box and test the diodes with a multimeter set to the diode function to confirm failure.
Step 5
The final confirmation is to compare the open-circuit voltage (Voc) and short-circuit current (Isc) of the suspect panel with a known good panel under the same sunlight.
DIY vs Professional Costs
| Repair Type | DIY Cost | Professional Cost | Time Required |
|---|---|---|---|
Monitoring & Visual ID | $0 | $150–$400 | 30 min |
Bypass Diode Replacement (Expert DIY) | $10–$50 | $400–$800 | 2-4 hours |
Full Panel Replacement | $300–$800+ | $500–$1,200+ | 3-5 hours |
When to Call a Professional Solar
- The moment you notice a panel consistently underperforming in your monitoring app.
- If you see any physical damage, burn marks, or discoloration on a panel.
- If you are not 100% comfortable and properly equipped to work safely on your roof.
- If you don't have the electrical knowledge or tools (like a multimeter) to safely diagnose the issue.
- If your panel is still under warranty – attempting a DIY repair will likely void it.
Prevention Tips
- Regularly trim any trees or vegetation that could cast shadows on your panels.
- Check your monitoring app at least once a month to spot underperforming panels early.
- When installing, ensure there's a proper air gap (a few inches) between the panels and the roof for ventilation.
- Clean your panels once a year to remove dirt and grime, which can help them run cooler.
Frequently Asked Questions
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