Will spring rain wash pollen off the modules, or do we need a clean?

The short answer

Rain helps but is often not enough. NREL saw up to 15% performance loss at peak pollen season on five North Carolina plants.

Plain explanation

NREL researchers studying five utility-scale plants in North Carolina found spring pollen reduced performance at every site, by as much as 15% in peak season. Rain washed away some pollen but did not fully restore performance; without planned cleaning, annual losses can be on the order of 10%. Plan a spring check in pollen-heavy areas rather than assuming rain finishes the job.

Steps from the source

Expect pollen losses in tree-heavy regions even with regular rain
Check performance after peak pollen; clean if it stays down
Bird droppings still need a spot clean regardless

"the performance of the solar panels decreased by as much as 15% during peak pollen season"

Word for word from the source.

Source

NREL news: Research Finds Rain Not Enough To Wash Pollen From Solar Panels, Body: performance decreased by as much as 15% during peak pollen seasonwww.nrel.gov ↗

Where installers ask this

General guidance based on the manufacturer's manual or the named source. Always follow the current manual for your exact model and your national code. DC and AC electrical work is for qualified installers only. Not affiliated with or endorsed by any brand named; trademarks belong to their owners.