Problem: Your solar panels should always be operating at 100%, maximizing the amount of electricity you capture. But periodic dirt/dust building prevents this, especially here in California with wildfires and our climate.
We don’t recommend cleaning them DIY - using regular water will leave streaks that make this situation worse. It’s important to use deionized water, which removes all minerals/particles from the water and prevents streaking.
Once a year is what we recommend. If you're near a construction zone or the freeway, doing it twice a year would be best.