How much does dust affect the output of my PV system?

Detailed studies have been conducted on this subject, concluding that dust does not have a significant impact on PV systems. This is perhaps surprising, but washing the panels with tap water in places where there is a high concentration of calcium (such as Alice Springs) can actually have a more negative effect than dust. The arrays at the DKA Solar Centre are washed once a year by a specialised company who use a reverse osmosis filtration system to treat their water before using it to wash the solar modules.