Solar Panel Cleaning Brush A transparent glass cover protects the PV cells in a solar panel. Ideally, you should clean the glass surface with non-abrasive cleaning tools like a soft bristle brush or squeegee. Avoid using wire brushes, roof rakes or any other tools that may leave scratches. You can wash solar panels with a garden hose, but you should never do this when they are hot since the drastic temperature change can crack the glass. Keep in mind that solar modules may still be hot after sunset, especially on summer days. Make sure you have a clean water supply when cleaning your panels. Washing your panels with hard water will leave behind a mineral layer after the water evaporates, defeating the purpose of the cleaning process.