How to Identify Solar Panel Hotspots

Hotspots are one of the most damaging faults a solar panel can develop. They occur when one or more cells in a panel overheat, creating localised thermal stress that accelerates degradation and can even cause permanent physical damage.

What causes hotspots?

The most common causes include:

• Micro-cracks — tiny fractures in silicon cells, often from manufacturing, transport, or installation. They may not be visible to the eye but create resistance that converts to heat.
• Cell mismatch — when cells in a string have different electrical characteristics, weaker cells can become reverse-biased and overheat.
• Persistent shading — if part of a panel is consistently shaded (by debris, bird droppings, or nearby objects), the shaded cells can become hotspots.

Why hotspots matter

A hotspot doesn't just reduce output from the affected cell — it can damage the encapsulant material, cause delamination, and permanently reduce the panel's output. In extreme cases, hotspots can present a fire risk.

Research shows that hotspots can cause 5–20% performance loss depending on severity and how many panels are affected.

Can you spot hotspots yourself?

Usually not. Some signs include:

• Browning or discolouration on the panel surface
• Visible bubbling in the panel encapsulant
• Unexplained drops in production from specific strings

However, most hotspots are invisible to the naked eye. Thermal imaging (infrared inspection) is the definitive way to identify hotspots — the overheating cells show up clearly as bright spots on a thermal camera.

When to get a thermal inspection

Consider thermal inspection if:

• Your system is more than 7 years old
• You've noticed a production decline beyond normal degradation
• You're in a hot climate with high thermal cycling
• You've had hail or storm damage

Use PanelAudit's Solar Loss Checker to estimate whether your system's profile suggests hotspot risk.