Wash Solar Panels?

Solar panel systems are intended to be largely maintenance-free, especially here in the Northwest where regular rains provide natural cleaning.

But we haven't had much rain the last few weeks, and I noticed some bird droppings on our panels, so I was curious if a manual cleaning would make much of a difference in power output.

This morning (before 9:00 AM), I did a quick hose spray and towel wipe down. I noticed dirt collects a little more at the bottom edge of each panel.

Now we can compare the energy output of two consecutive days with the same clear, sunny weather and similar high temperatures:

Dirty: 20.98 KWH (July 24, high 78°F)

Clean: 21.70 KWH (July 25, high 80°F)

The cleaner panels appear to eke out a few more electrons (+3%), restoring production to the same level as the brand-new system last year.