A solar thermal inspection uses infrared cameras to find faults in solar panels that are completely invisible to the naked eye. Hotspots, microcracks, delamination, and bypass diode failures all produce measurable heat signatures — and a thermal camera captures them clearly, even when the panel looks perfectly normal from the ground.

This guide explains exactly what happens during a thermal inspection, what faults it can and can't detect, how to read the results, and how to decide whether the cost is justified for your system.

What is a solar thermal inspection?

A thermal inspection (also called a thermographic survey or infrared inspection) uses an infrared-sensitive camera to measure the surface temperature of every panel in your array. Because failing solar cells generate more heat than healthy cells, a thermal image clearly reveals where problems exist.

The technique is well-established in large-scale commercial and utility solar: it's the standard method for identifying panel faults in multi-megawatt solar farms, where manual inspection of thousands of panels would be impossible. In residential solar, adoption has increased as drone technology has made the process faster and cheaper.

A thermal inspection doesn't interfere with your system and requires no access to your roof. The camera operator — standing on the ground or flying a drone — captures images of each panel under operating conditions, then analyses the thermal patterns to identify fault signatures.

What can thermal imaging detect?

Thermal imaging is highly effective at finding heat-producing faults. The main categories:

Hotspots are the most common finding. A hotspot occurs when one cell in a panel produces less power than its neighbours — due to a microcrack, soiling, or a manufacturing defect — and absorbs the current from surrounding cells as heat instead of converting it to electricity. Hotspots appear as bright warm patches on the thermal image, typically 5–30°C hotter than the rest of the panel.

Hotspots reduce panel output and, if severe, can permanently damage the cell and surrounding encapsulant. Early identification allows the fault to be recorded and a warranty claim initiated.

Delamination occurs when the layers of a panel (glass, encapsulant, cells, back sheet) separate. The air gap created changes the thermal characteristics of the panel, showing as a cooler region in the thermal image. Delamination allows moisture ingress and accelerates degradation.

Bypass diode failure is identifiable as an entire cell string within a panel appearing uniformly warmer or cooler than expected. Bypass diodes protect cell strings from hotspots — when they fail, a third of the panel's cells stop contributing to production. This is a repairable fault in some panel designs.

Complete cell or panel failure shows as an entire panel or string appearing significantly different in temperature to its neighbours. This could indicate a wiring fault, a failed junction box, or complete cell failure.

Shading effects are also visible — even intermittent shading from chimneys, aerials, or nearby vegetation shows clearly in the thermal data when inspection is done at the right time of day.

Soiling patterns (localised dirt or bird droppings) create cooler patches that can be confused with cell faults. An experienced inspector knows the difference — soiling creates diffuse edges while cell faults create sharp, localised hot spots.

What thermal imaging cannot detect

Thermal imaging is powerful but not a complete diagnosis:

It cannot detect PID (Potential Induced Degradation) in its early stages. PID reduces cell efficiency electrostatically without creating significant heat differentials until the degradation is advanced.

It cannot detect slow, uniform degradation. If all cells in a panel are degrading at the same rate, no temperature difference is visible. Uniform degradation below a performance threshold requires comparison against baseline monitoring data, not thermal imaging.

It cannot detect wiring faults between panels and the inverter unless they're severe enough to cause localised heating.

It cannot identify inverter problems — the inverter is not a target of thermal imaging.

A thermal inspection is most useful when combined with monitoring data analysis. If your monitoring shows underperformance but no single panel is obviously the culprit, the thermal inspection finds the physical cause. If monitoring looks normal but you want peace of mind for an ageing system, thermal imaging provides baseline documentation.

When is a thermal inspection worth doing?

A thermal inspection makes financial sense in these situations:

Your monitoring shows underperformance. If your system is producing 10%+ below expected output and you've ruled out obvious causes (dirty panels, shading, inverter faults), a thermal survey identifies which panels are responsible.

Your system is 5+ years old without any inspection. Faults can develop gradually. A thermal inspection at the 5-year mark establishes a baseline and catches early-stage problems while they're still covered by product and performance warranties.

Before a warranty expires. If your system is approaching the end of its product warranty (typically 10–12 years), a thermal inspection gives you the documentation to make a claim before coverage expires.

When purchasing a property with existing solar. A pre-purchase thermal inspection reveals the condition of the system before the sale completes. The cost of inspection is trivial compared to discovering a significant fault after purchase.

After a major weather event. Hail, high winds, or severe storms can cause microcracks that aren't visible but reduce output. A post-event inspection documents any damage for insurance purposes.

Coastal or high-humidity locations, after 3+ years. These environments accelerate junction box degradation and PID, making earlier inspection worthwhile.

The inspection process, step by step

Before the inspection

The inspector needs optimal conditions to produce reliable results. Solar panels must be actively generating electricity during the inspection — the fault detection relies on operating temperature differences, not just ambient temperature. The ideal conditions are:

Clear skies or high, thin cloud (enough irradiance to produce at least 400–500 W/m²)
Panels warmed up for at least 2 hours after sunrise
Low wind (which can cool panels unevenly and mask temperature differences)
No recent rain (wet panels change thermal characteristics temporarily)

Your inspector will typically schedule the inspection for mid-morning to early afternoon in your climate and season. They may reschedule if weather conditions are unsuitable — this is a sign of a thorough inspector, not inconvenience.

The inspection itself

Ground-based inspection uses a handheld or tripod-mounted infrared camera. The inspector photographs each panel section from the ground, typically from multiple angles to avoid reflections and blind spots. For a standard residential system of 6–12 kW (15–30 panels), this takes 45–90 minutes on-site.

Drone-based inspection uses an infrared camera mounted on a drone. This is faster (20–30 minutes of flight time for most residential systems), provides consistent overhead angles for each panel, and accesses panels on difficult rooflines without scaffold. Many inspection companies now use drones as standard.

The inspector will also check the inverter and visible wiring during the site visit, and may take a record of your monitoring data output for comparison.

After the inspection: understanding your report

A quality inspection report should include:

Thermal images of every panel, annotated to show fault locations. Images should show both a visual photograph and the corresponding thermal image side by side.

Fault classification for each identified issue. Standard IEC 62446-3 classifications distinguish between:

Class 1 (minor): temperature difference 10°C above ambient — monitor, recheck
Class 2 (moderate): 10–40°C above ambient — investigate, consider repair
Class 3 (severe): 40°C+ above ambient — immediate action required, safety risk possible

A summary table listing all identified faults, their location, classification, and recommended action.

Performance impact estimate: a rough estimate of how much output the identified faults are costing you annually.

Recommendations for each fault: monitor, clean, repair, warranty claim, or replace.

Ask your inspector how they classify faults and what threshold they use — if a report lists dozens of "faults" with no severity classification, it may be designed to alarm you into unnecessary repairs rather than guide your decision-making.

What happens after an inspection?

The actions available depend on what's found:

Minor hotspots (Class 1): Document, monitor, and recheck in 12–18 months. Many minor hotspots stabilise rather than worsen.

Significant hotspots (Class 2–3): Submit a warranty claim if within the product or performance warranty period. Bring the thermal report and your monitoring data as supporting evidence.

Delamination: Warranty claim where applicable. If out of warranty, panel replacement may be necessary — a cost worth weighing against the panel's remaining productive life.

Bypass diode failure: Some manufacturers will repair or replace panels with bypass diode faults. Others may offer replacement under warranty. Worth contacting the manufacturer directly with the thermal evidence.

Soiling identified as a fault cause: Professional cleaning — a much cheaper fix than panel replacement.

Wiring faults: A qualified solar electrician should investigate and repair DC wiring issues found during inspection.

How to choose an inspection provider

The quality of solar thermal inspections varies. Some points to look for:

Thermography certification. The inspector should hold a recognised infrared thermography qualification — Level 1 thermographer as a minimum. This certification ensures they understand how to capture images correctly (emissivity settings, viewing angle, atmospheric correction) and can interpret temperature data accurately.

IEC 62446-3 compliance. This is the international standard for solar photovoltaic system inspection using thermal imaging. Reports should reference this standard.

Clear report format. Ask to see a sample report before booking. A useful report includes both thermal and visual images side by side, fault classification, and specific panel locations.

Drone operator certification (if using drone). In the UK, drone operators need CAA certification (A2 CofC or GVC depending on proximity to people and property). In Australia, CASA certification. A professional inspector will confirm their regulatory status.

Experience with residential systems. Commercial solar inspection specialists don't always have experience with the specific fault patterns common in residential PERC and microinverter systems. Ask how many residential inspections they've done.

Check review platforms like Checkatrade (UK), Trustpilot, or Google Reviews for real owner experiences.

Typical inspection costs

System size	Ground-based	Drone-based
Up to 4kW (10 panels)	£120–£200	£150–£250
4–10kW (10–25 panels)	£150–£300	£200–£350
10–20kW (25–50 panels)	£200–£400	£250–£450

Australian pricing is broadly similar in AUD. US pricing runs $150–$500 depending on location and system size. Costs in southern Europe (Spain, Portugal) are generally lower.

Some inspection companies include a free monitoring data review before the site visit, which helps them focus the inspection on likely fault areas and improves overall value.

The ROI calculation

For a typical 6kW residential system generating 5,500 kWh per year:

A 10% performance loss = 550 kWh/year lost
At $0.25/kWh (export or self-consumption value), that's $137.50 per year
Over 10 years remaining warranty life: $1,375 in lost production
Inspection cost: $200–$350

If an inspection finds and enables you to claim for faults causing even a 10% loss, the financial return is positive in roughly 2 years. If the faults are severe enough to warrant manufacturer replacement panels — worth $200–$500 per panel — the ROI is substantially better.

The less obvious benefit is documentation. A thermal inspection report is your evidence if you need to make a warranty claim. A manufacturer can dispute a warranty claim based on monitoring data alone; a professional thermographic report signed by a certified thermographer is much harder to dispute.

Doing it yourself: what's possible

Handheld infrared cameras are available for under $500 (FLIR One, Seek Thermal), and some experienced DIYers use these to identify obvious hotspots. The limitations:

Handheld cameras have lower resolution and thermal sensitivity than professional equipment
Correct emissivity settings and viewing angles matter significantly — errors lead to false positives and missed faults
Roof access is required for ground cameras if panels aren't visible from street level
A DIY scan carries no evidential weight for warranty claims

For your own information, a consumer thermal camera can give you a rough picture. For documentation, insurance, or warranty purposes, a certified professional inspection is necessary.

Summary: should you get a thermal inspection?

Yes, if:

Your system is 5+ years old with no inspection history
Your monitoring shows underperformance you can't explain
You're approaching the end of your product warranty (typically year 10–12)
You've had a significant weather event (hail, storm)
You're buying a property with an existing solar system

Probably not urgent if:

Your system is under 3 years old with no monitoring anomalies
Your output tracks closely to installer estimates
You've had an inspection within the last 3–4 years

For most systems, a thermal inspection every 5 years represents a sensible maintenance cadence — comparable to a boiler service or electrical inspection in cost and purpose.

Solar Thermal Inspection: What to Expect and Is It Worth It?