Calcom Blog


February 27, 2019

Soiling of solar PV modules will degrade system performance, particularly In California’s agricultural regions where tilling and harvesting operations stir up dust. One of the most common questions we get is, “How frequently should we clean our solar panels?” Let’s take a look at a recent soiling analysis we conducted to help answer that question.

CalCom Energy uses real-time monitoring to track solar production data at sites within our asset management portfolio. We measure actual solar production against weather-adjusted production estimates. If a system is underperforming and equipment malfunction is ruled out, we can quantify the impact of soiling.

The chart below demonstrates the loss of performance on a system that was not being cleaned regularly. Over a four-month period, soiling reduced the performance of this 1MW system by half:

Expected solar production during this four-month stretch was estimated at 839,000 kWh, while actual production was measured at 597,000 kWh, a production loss of about 242,000 kWh. While value of lost production varies by site, we calculated this system’s value at $0.12/kWh, which yields a total production loss of $29,040, or $232/day.

Although some soiling loss between washings is unavoidable, monthly washings for three months would’ve reduced this system’s loss to about $6,290, or $50/day. When the system owner asked CalCom to begin cleaning on their behalf, the increase in system performance was dramatic and instantaneous:

So when should we wash our modules? Once a month is a good rule of thumb, but bear in mind:
• It will depend on the cost of a washing, and the value of your solar production. This is something that CalCom will be able to help you determine.
• Optimal system performance is particularly important between the months of March and October, during which over 80% of solar production is generated.

Contact CalCom today for a free soiling analysis of your system – we can shine up your panels and ensure top performance!

By Brendan Trimboli