Check the system instructions before choosing a schedule
Find the module model, installer paperwork and any lease or maintenance agreement. Those documents can specify cleaning restrictions, inspections or who is allowed to carry out work. If another company owns the system, confirm permission before booking.
For example, Canadian Solar explains that sufficient tilt and rain may reduce the need for cleaning on some installations. That is product guidance, not a promise that rain will clean every array. It also shows why a blanket monthly or twice-yearly recommendation does not suit every homeowner.
Use these conditions to decide when to look again
The useful question is what has changed since the last inspection or clean. Being in Fresno, Clovis or Madera does not by itself establish what is on your glass.
Scroll sideways to see all columns.
| Condition at your property | What to check from the ground | Next step |
|---|---|---|
| Dust-producing work nearby | A fresh film or heavy bands after field work, road work or construction | Record the timing and arrange assessment if buildup persists. |
| Bird activity | Birds entering beneath panels, droppings or nesting material | Ask about nest activity and exclusion as well as glass cleaning. |
| Sprinkler overspray | White marks in the spray path | Correct the spray source; ask whether deposits need separate treatment. |
| Trees or new shade | Leaves, sap or a shadow that was not present before | Separate debris removal from shade or tree-management work. |
| Recent substantial rain | Whether visible material actually moved | Do not assume a rainfall event was a complete cleaning. |
| Low-slope or sheltered modules | Deposits at edges or areas rain does not reach | Include the array layout and photos when discussing a schedule. |
Monitoring data gives clues, not a diagnosis
Keep a record of cleaning dates, rainfall, unusual dust and any inverter alerts. Compare daily energy in kilowatt-hours, rather than a single power reading. Choose dates close together with similar weather and no obvious change in shade or system availability.
Temperature, sunlight, clouds, smoke, inverter limits and missing data can all affect the comparison. A decline during dry weather may be consistent with soiling, but a step change can also come from new shading or other causes. Rain failing to restore output does not prove an electrical fault. Ask the system provider to investigate unexplained changes.
Plan around work that will make the panels dirty again
If dusty work is about to happen beside the array, discuss whether to wait until it finishes. For an exterior-service bundle, agree the order of roof work, gutters, solar glass and windows so later washing does not immediately re-soil finished areas.
A useful schedule records the reason for each visit and a point to reassess. If little material has accumulated by the next proposed date, discuss extending the interval. If one exposure repeatedly causes buildup, address that source where practical instead of simply adding more visits.
What to send for a cleaning recommendation
You do not need to climb onto the roof to make an informed inquiry.
- Property address, approximate panel count, roof material and number of stories.
- Ground-level photographs showing the array and any obvious spots or debris.
- Last known clean, recent rain and nearby activities that may have raised dust.
- Any birds entering the array or old bird mesh already fitted.
- The module model and maintenance restrictions, if you have them.
- A screenshot showing the time range and alert message if production is the concern; never send monitoring passwords.
When to call the installer first
Cracked glass, damaged conduit, visible burning or an inverter fault needs the system provider or an appropriate solar electrical contractor. Keep clear of damaged equipment and do not touch connections to investigate. A cleaning visit cannot certify the system or replace electrical diagnosis.
CA Solar Wash can discuss accessible cleaning, bird protection and a photographed visual check. Request those services by name and ask what is included. No production increase or universally correct cleaning interval is promised.
