Some panel cleaning jobs are more substantial than others, so it is really important to ensure that the correct cleaning kit is used. In this case there was a substantial build up of dirt, as well as lichen growing on the panels themselves.
When dirt builds up to these kind of levels, there is a very substantial reduction in the amount of electricity being produced and the amount of income being received from the solar PV system. It is important to ensure that, if possible, panels are cleaned regularly enough not to let it reach this stage.
With the correct equipment it is possible to return the panels to their original condition and therefore to substantially increase the amount of revenue they are providing. Regular solar panel cleaning and system maintenance will ensure you get the best return on your investment.