At Solar Beam, we only clean the panels with De-ionized water (ultra filtered) to ensure no minerals or other contaminants are used. Simply using a water feeding brush and a squeegee, we achieve the shine that is wanted and the increase in efficiency that is needed to make our service make cents for you.
Do not use any chemicals on the panels! Solar panels already have a coating on them to help reduce material build up, by using chemicals you will deteriorate the protective film on the panel and create a less efficient panel. If you don't use Solar Beam for your cleaning service, make sure you never have someone else use chemicals to clean the panels.
Do not use a scraper on the panels as it causes damage to the protective layer, a window squeegee is perfect for the panel.