Solar Panel Hot Spots: Causes, Damage, and How to Fix Them
Hot spots are one of the most destructive solar panel faults and one of the most preventable. Here is what causes them, how to find them, and what repairs cost in Australia.
Hot spots are among the most destructive problems a solar panel system can develop — and most homeowners have no idea they are happening. Unlike a blown fuse or a dead inverter, a hot spot does not trigger an alarm or error code in your monitoring app. It silently degrades individual cells, reducing your system’s performance permanently, and in severe cases poses a genuine fire risk.
Understanding what causes hot spots, how to identify them, and how to prevent them is essential knowledge for any Australian solar panel owner.
What Is a Hot Spot and How Does It Form?
A solar panel is made up of many individual photovoltaic cells — a standard 60-cell or 72-cell panel connects these in series strings, with bypass diodes protecting small groups of cells. When all cells in a string are working correctly, current flows uniformly and the panel operates at its rated temperature.
A hot spot forms when one or more cells produce less current than the others in their string. Because the cells are in series, the full current generated by the functioning cells must still flow through the underperforming cell. The underperforming cell cannot accept this current as electricity — it dissipates it as heat instead.
The result: a small area of the panel reaches temperatures that can exceed 100 to 150 degrees Celsius while the surrounding panel surface sits at 40 to 60 degrees. At these temperatures the ethylene vinyl acetate (EVA) encapsulant laminate begins to degrade and yellow, cell metallisation (the silver contact grid) can crack or delaminate, the backsheet can discolour and eventually burn, and in extreme cases the glass can crack from thermal stress.
Once hot spot damage has occurred to the laminate or cells, it is irreversible.
The Most Common Causes in Australian Conditions
1. Partial Shading from Bird Droppings
This is the number one cause of hot spots in Australian residential systems. A single bird dropping that covers even part of one cell creates a classic partial shade condition. Because the dropping is opaque, the shaded cell produces little or no current while the rest of the string generates full output.
The bypass diodes activate to protect the affected cells, but if the dropping is small enough to affect only part of a cell, the bypass diode may not trigger — meaning the partial shade condition forces current through the partially shaded area continuously.
Australian research indicates bird droppings are the leading cause of unscheduled warranty claims related to cell damage in systems under 5 years old.
2. Lichen and Organic Growth
Unlike bird droppings, lichen grows slowly and its shading effect increases gradually over months and years. The combination of persistent shade (lichen does not wash off in rain) and the slightly acidic surface the organism creates means lichen-covered cells develop hot spots over time without a visible triggering event.
Roof-pitch angles under 15 degrees and shaded or south-facing panels in humid climates are the highest risk for lichen-driven hot spots.
3. Micro-Cracks (Invisible to the Naked Eye)
Micro-cracks in silicon cells can develop from installation damage (dropped panels, improper panel walking during installation), hail impact (even hail that does not visibly crack the glass can crack underlying cells), and thermal cycling stress — extreme temperature variation common in inland Australia causes expansion and contraction that stresses cell metallisation.
A micro-cracked cell has reduced current-carrying capacity. The greater the crack, the more it mimics a shading condition — forcing bypass and generating heat.
4. Manufacturing Defects
Latent manufacturing defects — poor solder joints, misaligned cell busbars, substandard EVA lamination — can manifest as hot spots within the first 1 to 5 years of operation. Quality-certified panels from established manufacturers have significantly lower defect rates than lower-cost alternatives.
5. Soiling and Dust
Non-uniform soiling — where dust accumulates more heavily on parts of the panel than others — can create partial shading similar to bird droppings. This is particularly relevant in dusty inland Australian environments where windborne dust deposits unevenly, often concentrating at the leading edges and lower portion of a tilted panel.
6. Shading from Trees, Structures, or Neighbouring Buildings
External shading is a design issue rather than a maintenance issue, but any regular partial shading condition creates ongoing hot spot risk in the shaded cells.
How to Detect Hot Spots
Method 1: Thermal Imaging (Most Reliable)
An infrared camera or thermal imaging drone scan is the gold standard. A qualified inspector scans the array while it operates under full sunlight (typically between 10am and 2pm). The thermal image reveals cell temperature distribution across every panel.
What to look for in the report: point anomalies (a single bright spot on a panel) indicate bird dropping or micro-crack hot spots; stripe anomalies (a line of elevated temperature across a cell row) indicate a cracked cell or series resistance issue; panel-level anomalies (where one full panel is hotter than surrounding panels) suggest a bypass diode failure or delamination.
Thermal imaging services cost $150 to $350 for a standard residential array and are available from specialist solar inspection companies, increasingly offered as a drone service in metro areas.
Method 2: String-Level and Module-Level Monitoring
Systems with SolarEdge optimisers or Enphase microinverters monitor output at the individual panel level. An underperforming panel producing significantly less than its neighbours under the same conditions may have an active hot spot.
Log into your monitoring portal and compare panel-by-panel output on a clear day. Any panel producing more than 10 to 15% below its array neighbours warrants investigation.
Method 3: Visual Inspection
While micro-cracks and early-stage hot spots are invisible, advanced hot spot damage is often visible from ground level with binoculars: brownish or yellowish discolouration on the cell visible through the glass (EVA browning), dark patches on the backsheet (backsheet degradation), visible cell cracking in the pattern of a cracked windscreen, and bubbling or delamination visible as raised areas on the panel surface.
If you can see any of these signs from ground level, the affected panel is likely permanently degraded.
Prevention: The Maintenance Connection
The strong link between hot spots and preventable soiling means that regular professional cleaning is also hot-spot prevention:
| Preventable Cause | Prevention Method |
|---|---|
| Bird droppings | Professional cleaning every 6 to 12 months; bird mesh installation |
| Lichen/organic growth | Annual inspection; lichen treatment (professional application only) |
| Non-uniform dust soiling | Regular cleaning, particularly in dusty inland areas |
| Vegetation shading | Annual inspection; tree trimming |
Bird mesh installation specifically eliminates the most common hot spot cause in Australian conditions. A bird proofing system typically costs $400 to $900 for a 6.6 kW array — less than the cost of a single panel replacement, and it prevents the problem from recurring.
What to Do If You Suspect a Hot Spot
- Check your inverter monitoring for any panels flagged as underperforming, or any unexplained output drops
- Inspect panels from ground level with binoculars for visible discolouration or cell damage
- Book a thermal imaging inspection — do this before or after cleaning, not during, as a wet panel surface can mask thermal anomalies
- If damage is confirmed, check your warranty — most Tier 1 panel warranties cover hot spot damage caused by manufacturing defects
- Get a quote for panel replacement from your original installer or a qualified solar technician
Do not continue operating a system with suspected DC wiring exposure or backsheet damage — these conditions can lead to arc faults and fire.
Hot Spot Repair and Replacement Costs
| Issue | Typical Cost (Installed) |
|---|---|
| Thermal imaging inspection | $150 to $350 |
| Single panel replacement (standard 400W panel) | $300 to $600 |
| Two-panel replacement | $500 to $900 |
| String-level diagnosis and repair | $400 to $800 |
| Bypass diode replacement (module-level, if accessible) | $200 to $400 |
| Inverter repair related to ground fault | $500 to $1,500 |
| Full array thermal imaging + report (drone) | $250 to $500 |
Summary
Hot spots are a silent but serious threat to solar panel performance and longevity. They are caused by partial shading — most commonly from bird droppings in the Australian context — along with micro-cracks, lichen, and manufacturing defects. Left undetected, they permanently degrade cells and reduce your system’s output for its remaining lifespan.
The prevention strategy is simple: keep panels clean, install bird mesh if your system experiences regular fouling, and book an annual inspection that includes a panel-by-panel output check or — ideally — a full thermal imaging scan every 2 to 3 years.
Catching a hot spot early means catching it before the damage is permanent.
Last updated: April 2026. Cost estimates are indicative and reflect Australian market conditions. Always obtain written quotes from licensed installers.
Frequently Asked Questions
A hot spot is a localised area of a solar panel that overheats, typically 20 to 80 degrees Celsius above the temperature of the surrounding cells. It occurs when one or more cells in a panel are shaded or underperforming, causing the full current from unaffected cells to be forced through the damaged area as heat. Hot spots can permanently damage cells, degrade EVA laminate, and in severe cases cause fire.
Yes. Bird droppings are one of the most common causes of hot spots in Australian residential systems. A single dropping that covers part of one cell creates a partial shade condition. The bypassed current concentrates heat at the shaded point. This is why professional cleaning specifically addresses droppings rather than simply rinsing the panel surface.
The most reliable detection method is thermal imaging (thermography). A licensed technician uses an infrared camera to scan panels while they are operating. Temperature differentials of 20 degrees or more above the panel average indicate a hot spot. Some monitoring systems (SolarEdge, Enphase) flag underperforming panels at the module level, which can also suggest hot spot conditions.
Minor hot spots caught early via thermal imaging can sometimes be addressed before they cause permanent damage. However, if the EVA laminate has browned, the cell has visibly cracked, or the backsheet has discoloured, the panel is permanently degraded. Replacement is the only effective remedy in these cases. Most quality panel warranties cover hot spot damage as a manufacturing defect.
Thermal imaging inspections cost $150 to $350 for a standard residential array. Panel replacement for a hot-spot-damaged panel runs $300 to $600 installed. If an entire string is affected, string-level diagnosis and repair can reach $800 to $1,500. Inverter damage caused by hot-spot-related ground faults can cost $1,000 to $3,000 to repair or replace.