Before cleaning the panels yourself, you should consult with your installer about the warranty conditions. Some solar panel manufacturers could terminate the warranty if any self-cleaning is done.
For general cleaning, you can just use a normal garden hose to wash the face of the panels. You should do this in the morning or evening. Also, avoid spraying them with cold water while they are hot because that might damage them.
Moreover, If the panels need some more cleaning that the hose cannot provide, you can use a sponge with soapy water to scrub them. You can also get the services of a cleaning company. This is advisable if the panels are too high or need a more thorough cleaning.
