Solar panels require little to no maintenance to continue operating for years. Cleaning once or twice a year doesn't hurt. In the event of severe smog or ash from wildfires, hosing the panels off isn't a bad idea, but we would never encourage you to climb up on your roof or do anything unsafe. If you're going to use water to clean the panels, do it either early in the morning or later in the evening, so that you're not hitting them with cold water while they're directly in the hot sun.
Check out our blog post for more details.