As we’ve seen so far, the short answer is, “The impact of dirty solar panels on solar power production depends on various factors.” But we’re interested in the long answer, right? Let’s dig into the science and math a bit:
An experiment involving solar panels on a low-slope roof sought out the difference in energy output before and after a thorough cleaning.
The researchers found an average 3.5% boost in energy production (the amount of power produced over time) after cleaning the panels using a soft rag and water. The implication here is that the energy yield increase was low, despite the high amount of dirt accumulation.
Things became interesting when heavy rain did the cleaning job. The average performance increased by only 1.9% after rainwater pounded on the dirty panels. What does that mean? A good shower from the skies can take care of some cleanup, but it’s not as effective as the proper equipment and some elbow grease.
You may want to check how much your dirty solar panels are costing you in terms of energy generation. Here’s a simple formula for determining the value of solar panel cleaning:
Yearly Energy Production (kWh) × Production Loss From Dirty Panels × Electricity Cost per kWh
For example, if your residential solar energy system can produce 10,000 kWh of electricity per year, and you assume a 5% loss of production due to panels being dirty, and you pay $.20 cents per kWh for electricity from your utility, your yearly cost of electricity loss from dirty panels is as follows:
10,000 × .05 × .20 = $100
A 5% electricity production loss might not sound like a lot, but it can definitely add up, and suddenly you’re paying way more to your utility company on your electricity bill than you need to be.