Solar panels are usually self-cleaning – light rain will wash off superficial dust and leaves – but if your panels don’t have much of a tilt, or if they build up quite a lot of bird poo over the year, then they may need a bit of extra help.
Tips for cleaning your solar panels
Before you start, always shut down your system according to the manufacturer’s instructions; if you can’t access your panels from the ground and you don’t have the right sort of safety equipment and/or training, call in a professional.
Use the right tools
You need a soft brush and a squeegee – one with a plastic or rubber blade on one side and a soft sponge on the other – as well as a long hose with a nozzle that lets you reach the panels from the ground.
Choose the right time
It’s best to clean your panels early in the morning so the dew has already softened any deposits that may be there. An overcast day is best, too, as a bright or hot day will evaporate the water too quickly and this will leave smears. Brush off any leaves and other debris first.
Don’t use harsh sponges or detergents
Abrasive sponges or cleaning products will scratch the panel’s glass, which will create shadows and affect performance. All you really need is some clean water and a clean towel or soft sponge to work on stubborn areas.
Watch out for hard water
If your mains water is quite hard (it contains lots of dissolved minerals) then use rainwater as a final rinse if possible. Alternatively use your squeegee to remove as much of the water as possible so that the dissolved solids don’t leave streaks and form deposits once the water has evaporated.
If there’s oil
If there’s an airport nearby, or a busy road used by freight trucks, then you might find sooty or oily deposits forming on your panels. Alcohol is the best solution here (on the panels, not in you!).
Don’t worry too much
If there’s no visible dirt or deposits on your panels, then you can probably just leave them be – the odd rain shower is probably all you need.