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Cloudy days?
Still generating.
Myths · 4 min read · By the Lumenbeam energy team
The most common question we hear in Portland: “But does it work when it's gray?” Short answer: yes. Longer answer below.
Panels run on light, not heat
Photovoltaic cells convert photons, not temperature — they actually run slightly more efficiently when cool. An overcast sky still delivers diffuse light, and modern high-efficiency cells harvest it well.
What output looks like
Under heavy cloud, expect roughly a quarter to two-fifths of rated output; light overcast often yields more than half. Across a Northwest year, installers model this precisely — winter months contribute less, long summer days contribute far more, and the annual total is what your savings are built on.
Why our systems handle gray skies
We specify panels with strong low-light response, add optimizers so no shaded section drags the rest, and tilt arrays to catch maximum diffuse sky. Then monitoring proves it: customers watch generation on cloudy days in the app.
Curious what your roof would make?
Our free assessment models all twelve months — gray ones included.
