Lower solar generation does not by itself prove that panels need cleaning. Output can change with sunlight, outages and measurement coverage. Before arranging work, assemble five observations so the O&M team can decide what to inspect and how to evaluate the result.
First rule out an unfair comparison
A monthly total can fall even when the array has not developed a new defect.
1. Sunlight and conditions
Compare solar-resource information and relevant weather conditions for the selected periods.
2. Coverage and dates
Check that both data sets cover the same period and that missing intervals have not been treated as zero generation.
3. Downtime and restrictions
Review inverter and grid events, scheduled work and recorded output restrictions before attributing the difference to dirt.
Then assess shading and soiling evidence
These observations help target the site inspection. They are not a diagnosis from the dashboard.
4. Shading changes
Review recent changes around the array, including new obstructions, against the time of the observed reduction.
5. Surface condition
Use safe inspection evidence and available soiling measurements to assess deposits. Follow the module maker’s cleaning instructions and the site’s access rules.
Define how the cleaning result will be checked
Record the treated area, work date, method and findings. Compare subsequent operation with an appropriate reference and account for changed conditions. A higher total on a sunnier day cannot demonstrate the effect of cleaning by itself.
Create an evidence-based work order
Give the service team the observations and expected checks, then keep completion evidence in the site history.
Frequently asked questions
Should panels be cleaned every month?
There is no interval suitable for every site. Consider actual deposits, operating evidence, manufacturer guidance and safe access.
Does rain always remove the need for cleaning?
No universal assumption is appropriate. Check the actual surface condition and subsequent performance before deciding.
Organize the inspection and service follow-up
Solar O&M Management Software connects site history, planned maintenance and technician jobs. Use the evidence to assign the appropriate work and retain the completion record.
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References
- NREL: Time Series Analysis of Photovoltaic Soiling Station Data
- US DOE: Operate and Maintain an Existing Photovoltaic System
- IEA PVPS: Best practice guidelines for technical and economic KPIs
Information and sources reviewed: 8 October 2026