August 14, 2013

Is cleaning solar panels worth the time and effort? How much does dirt affect electric power generation?

A new study by UC San Diego reviewed solar panel efficiency during 2010’s 145 day drought here in California. The result? Less than a 0.05 percent efficiency loss per day for most residential systems – hardly enough to make cleaning worth it. Financial losses for larger commercial systems are greater, but not huge.

That said, we find it’s different for our ag clients – blowing dirt from tilling and harvesting can decrease panel efficiency by as much as 15-20%. It’s easy to know when that’s happening with our installations, as all offer daily (and hourly!) monitoring of electrical output. When you do see production decreasing, clean the panels.

Graph comparing Solar panels before and after washing​​

There are two easy ways to do this. Some growers install simple sprinkler systems that can be activated as needed for a quick wash. Some just use a portable water tank to hose off the panels 1-2 times a year. Plain water is enough to clean the panels of basic dirt. Bird droppings may require a bit of a scrub – we recommend using NO soap (or, aluminum safe soap). Use a long handled, soft brush. NEVER climb up onto the array.

CalCom does the routine maintenance on your system the first year, and we also offer ongoing yearly contracts to clean your inverters and panels and check all connections.