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Researchers Find Dirt Has Minimal Impact On Solar Panel Effectiveness

Typical solar panel systems don't need to be washed off in the middle of the summer, even though there's plenty of dirt collection on them.

— Engineers in San Diego say it may not make financial sense to spend money washing down rooftop solar panels.

Researchers at the UC Jacobs School of Engineering studied solar output of more than 185 solar panel systems in California in 2010. They found that dust did impact the panels' ability to produce electricity. However, lead researcher Jan Kliessl said the reduction wasn't enough to warrant spending money on a thorough washing.

"The accumulation of dirt that sometimes looks quite dramatic on solar panels has very little impact on how much energy they generate," said Kliessl.

The study found dirt reduced electricity production on typical residential and commercial systems by just greater than 7 percent. That only represents about $20 worth of generated electricity.

Kliessl said mounting panels at a greater than 5-degree angle helps reduce accumulation of dirt.

The study findings are published in the current edition of the online journal Solar Energy.

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