Should the solar panels of a solar power system be cleaned?

As long as the solar panels are mounted with a pitch of 10-15 degrees, most of the dirt should be washed of by the rain. When the solar modules are particularly dirty, and no rain is expected due to a dry season, it can be smart to clean the solar panels though. Cleaning the solar panels should be done with a soft cloth (to protect the coating) and ideally demineralized water.