How often should a solar farm be thermally inspected?
Owners ask this more than any other question, usually right after the first inspection has found more than they expected. The honest answer is that it depends on the plant, but there is a sensible default and a short list of exceptions.
The baseline: once a year
For an operating plant with no known systemic problems, one full-plant inspection a year is the common practice and it lines up with how most O&M contracts and performance reviews are structured. Timing matters more than people think:
- Before the annual performance review, so the reasons behind a performance ratio shortfall are on the table with the numbers, not investigated afterwards.
- Before, not after, a warranty milestone. Module product warranties and EPC defects liability periods have dates. Inspecting three to six months ahead leaves time to document and file a claim.
- In a stable season. Consistent conditions year to year make trends easier to read.
When twice a year is worth it
Some plants degrade or fault faster than average and the second inspection pays for itself. Common cases in Malaysia:
- Plants with confirmed potential-induced degradation (PID), where the affected population grows between surveys.
- Sites with heavy soiling from nearby agriculture, quarrying or construction, where the cleaning schedule needs evidence to justify its cost.
- Floating plants, where connector and cable faults develop quickly in a humid, moving environment and access for spot checks is poor.
- Plants with a history of connector or junction-box heating, which is a fire risk as well as a loss.
- Plants where the O&M contract has performance guarantees and both parties want mid-year evidence.
One-off inspections that should not be skipped
| Moment | Why inspect |
|---|---|
| Commissioning / provisional acceptance | Transport and installation damage is common and is the EPC's problem only until you sign. |
| End of defects liability period | Last chance to claim installation defects against the contractor. |
| Module warranty expiry | Diode failures and early degradation are claimable while the product warranty runs. |
| After lightning, flood, storm or fire | Insurance evidence, and separating event damage from pre-existing faults. |
| Acquisition, refinancing, change of O&M | A dated baseline everyone agrees on. |
| After a major repair campaign | Verify the work was done and the losses actually recovered. |
What about continuous monitoring?
Inverter and string monitoring is essential and it is not a substitute. Monitoring tells you a string is down. It does not tell you which of the modules in that string has a failed diode, which connector is heating, or that a block of modules is degrading faster than its neighbours while still producing. Periodic module-level inspection and continuous monitoring answer different questions, and mature operators use both.
A simple rule of thumb
Inspect once a year, timed before your performance review and any warranty date. Move to twice a year if the first inspection shows PID, connector heating or a repair backlog you cannot clear in one campaign. Add a one-off survey at every point where money or liability changes hands.