How to clean solar panels

Accumulated dirt can reduce the amount of sunlight absorbed by solar panels. The efficiency of solar panels can be improved by cleaning with the right methods. The need for a solar panel cleaning action can be determined based on visual inspection or a general downwards trend of the system energy generation. Note that in many cases it is not worth the investment to perform a professional cleaning. Only when there is no regular rain and the panel tilt is almost horizontal it might pay off.

Safety and electrical precautions

Once you decide to start cleaning make sure all safety precautions have been taken and the solar panel system is locked out for any energy release:

  1. Check the instructions of your solar panel manufacturer.
  2. Assess the accessibility and safety to clean your solar panels. In many cases, it is better to hire a professional dedicated cleaner. Especially when your solar panels are roof mounted. Many homeowner insurance policies do not cover homeowners working on roofs.
  3. Assure of dedicated safety equipment such as a safety helmet and a harness.
  4. Shut down the solar panel electrical equipment. Check your manufacturer handbook on how to ensure the electrical currents are disconnected. Ensure any AC and DC systems are switched off.
  5. Be aware that the cables on the roof still have dangerous voltages applied. Immediately stop if damages to cables are observed.
  6. Furthermore, broken panels and shorts in the system can get you electrocuted when applying water.


Cleaning steps and instructions

If all preparations are successfully completed the following steps can be executed for the actual cleaning:

  1. The best time to clean is the early morning when the panels are cool.
  2. Never stand on the panels and climb on the roof without safety gear.
  3. Remove all rough dirt such as leaves, bird poop, and sand from the panels.
  4. Initially do not use water to prevent the spread of the debris.
  5. After most rough dirt has been removed, water can be used to spray the panels clean.
    1. Avoid using a high-pressure water system as it can induce cracks on the panels' top layers.
    2. It is strongly recommended not to use detergents or soap as there can be unwanted side effects compromising the integrity of your solar panels.
    3. Consider using a special cleaning solution as tap water could reduce the power generation efficiency a little bit.
    4. De-ionized water with a (robotic) rotating brush is what is used by many professional cleaners.
    5. Do not clean with water below the panels wiring underneath can be affected. Therefore only clean the top of the panels.
  6. Use a soft brush (non-abrasive) or cloth and some water to clean problematic areas. 

After the cleaning actions have been performed the inverted can be switched on again. The energy generation can be compared with pre-cleaning levels. This analysis can be used to assess if and when a future cleaning is worth the investment.