Reverse osmosis (RO) water is the ideal option. If RO is not available, rainwater or tap water with low mineral content and a total hardness that is less than 75 mg/L may be used. Water with a significant amount of dissolved minerals, often known as hard water, leaves behind a. . Water quality: The quality of water is crucial when cleaning solar modules. Use deionized, or. . Listed below are important factors to consider before setting out to clean your solar panels with water, even if you intend to outsource the cleaning to professionals. High-pressure washing can damage weatherproof seals, cause water infiltration, and create invisible microcracks. However, in order to ensure maximum power output, cleaning of PV modules is recommended to be performed once a year (as a planned preventive activity), and can be also recommended as a result of a applicable on-a rasive and non ding. . When cleaning solar panels, it is recommended to use calcium-free water, such as distilled or softened water.