Why commercial solar owners need testing beyond the monitoring portal: what thermal imaging and IV curve testing each find, how the two work together, how often to test and what it costs. A monitoring portal tells a commercial owner how much the system produced; it rarely tells you why it produced less. Thermal imaging finds components that are running hot, such as damaged cells, failing bypass diodes and overheating connectors, while IV curve testing measures each string's electrical behaviour against what it should be. Used together, typically as a baseline at handover and then on a regular schedule, they find losses and safety risks that a portal averages away.
Why the monitoring portal is not enough
Commercial portals are useful, but they have blind spots:
- Averaging hides small losses. On a large array, one underperforming string can disappear inside the site total, especially on partly cloudy days.
- Alarms catch hard faults, not slow ones. An inverter reports when it trips or loses a string completely. A string that has lost part of its output usually raises no alert at all.
- Weather muddies comparisons. Month-on-month drops are easy to blame on cloud when the real cause is degradation, soiling or a failed diode.
- Heat is invisible in the data. A connector or isolator that is overheating may cause no measurable loss until it fails, and it is a fire and outage risk well before then.
For a business, lost production directly weakens the return the system was bought for, whether you modelled it in our commercial ROI calculator or in a formal business case. Unplanned shutdowns can also arrive at the worst time of year. That is why owners of larger systems treat testing as part of asset management rather than a response to a breakdown.
What thermal imaging finds
An infrared camera shows temperature differences across the array while it operates in strong, steady sunshine. Panels in good condition appear evenly warm; faults show up as distinct patterns. Scans are done at roof level or by drone, depending on the site, access and safety requirements. Typical findings include:
- Hot spots from cracked cells, including damage from hail, foot traffic or poor handling
- A warm strip or section across a panel, which often points to an activated or failed bypass diode
- Patchwork patterns across many panels in a string, which can indicate potential-induced degradation
- Overheating DC connectors, isolators and combiner terminals
- Soiling and debris patterns, for example downwind of roof vents or exhaust outlets
The strength of thermal imaging is speed and coverage: a whole roof can be scanned and the problem panels located precisely, which makes repairs quicker and more targeted.
What IV curve testing finds
An IV curve tracer briefly sweeps a string from short circuit to open circuit and records the current (I) and voltage (V) along the way. The shape of that curve is compared with the expected curve for the panel type, the number of panels, and the sunlight and cell temperature measured at the time. Deviations point to specific causes:
| What the curve shows | Likely cause |
|---|---|
| Current lower than expected across the curve | Uniform soiling, degradation, or an issue with the sunlight reference measurement |
| Voltage lower than expected | Bypassed cell groups, or fewer working panels in the string than designed |
| Steps or notches in the curve | Partial shading, cracked cells or mismatched panels |
| A flatter, rounded knee | Higher series resistance from corroded connectors or damaged cabling |
| No curve at all | An open circuit, such as a failed connector, blown fuse or disconnected cable |
Because it works string by string, IV testing produces hard numbers you can compare from one year to the next, which makes it the best way to track real degradation over the life of the system.
Using both tests together
The two methods answer different questions. Thermal imaging shows where something is wrong; IV curves show what kind of fault it is and how much output it is costing. A practical sequence on a commercial site is:
- Review the monitoring data and alarm history to identify weaker inverters or MPPT inputs.
- Scan the array thermally to locate hot panels, connectors and isolators.
- Trace IV curves on every string, or on the strings flagged by the data and the scan.
- Report the findings with images, curves, likely causes and a priority rating.
- Carry out repairs, then retest the affected strings to confirm the fix.
All of this involves live DC circuits and work at height, so it must be carried out by trained technicians and licensed electricians working to the site's safety requirements. Site staff should never open combiner boxes or isolators to take a look.
How often commercial systems should be tested
The right interval depends on system size, the roof environment and how much the output is worth to the business. A common approach is:
- At handover: a baseline thermal scan and IV curves, so every later test has a reference point
- Every year: a thermal scan, ideally on a clear day in the warmer months when sunshine is strongest
- Every one to three years: IV curve testing across all strings
- After an event: hail, a severe storm, roof works by other trades, or an unexplained drop in the portal
- Before key decisions: buying or leasing a building with solar, the end of a workmanship warranty period, or planning an expansion
Roofs exposed to dust, exhaust outlets or salt air may justify shorter intervals. If you are still designing a site, our commercial solar page explains how we plan systems around the way a business actually uses energy.
Costs and what affects them
In our energy market, a Thermal Imaging Inspection is listed from $990 and IV Curve Testing from $1,290, each for systems up to 100 kW. These are indicative starting prices confirmed after a site assessment, because roof access, array layout, the number of strings and any drone requirements vary from site to site. Larger systems are quoted individually. When weighing the cost, remember that on a commercial system even a modest loss of output left unnoticed for a year can add up to more than the test itself.
Next steps
If you own or manage a commercial system and its portal data has never been checked against real test results, request a quote for thermal imaging or IV curve testing and our commercial team will assess the site. If you are planning a new or expanded system, ask about baseline testing at handover so future results have something to be measured against.
Frequently asked questions
Does the system need to be shut down for testing?
Thermal imaging is done while the system operates normally, because faults only show up as heat when current is flowing. IV curve testing takes each string offline for a short time while the tracer is connected, so there is a small, temporary loss of production. We plan the sequence with the site so critical operations are not affected and strings are returned to service one at a time.
Can a drone scan replace a technician on the roof?
A drone is a fast way to scan large or hard-to-reach roofs and it reduces time spent at height, but it does not replace hands-on work. Connectors, isolators and combiner boxes still need close inspection, and IV curves must be measured at the strings themselves. Drone flights also have to comply with aviation rules and any site restrictions, which are checked before the visit.
Will the test results help with a warranty claim?
They can. Manufacturers generally want evidence rather than a feeling that output is low. Dated thermal images, IV curves compared with expected values and the serial numbers of affected panels give a clear, specific record. Whether a claim succeeds still depends on the warranty terms and the manufacturer's own assessment, but good test data makes that conversation far more productive.
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