Council's fact sheet says the Blue Gum High Forest around Pymble shelters native wildlife including the Grey-headed Flying Fox and Glossy Black Cockatoo. That is a good thing for the suburb and a less convenient one for a rooftop array below the trees. Droppings, pollen and dust all settle on the glass, and solar panel cleaning with purified water and no detergent clears them without leaving a residue behind.

Height is what sets a Pymble array apart. Council says Sydney Blue Gums reach up to 30 metres, and in the conservation areas those trees stand over one and two storey houses. Whatever comes down from them has a lot of air to drift through, so a panel can collect from trees that are not in your garden at all.
Council's tree guidelines rule out reducing bird or animal droppings as a reason to prune, and increasing natural light fails the same test. An owner therefore has limited say over what is above the panels, and more say over what stays on them. A dropping is opaque, and it blocks light to the cells beneath it until someone removes it.
Roof form makes the glass hard to check. Steeply pitched hipped and gabled roofs on large blocks mean that an owner standing in the garden rarely gets a useful view, and an array on a rear plane may be invisible from anywhere on the property.
Elsewhere the source of the dirt changes. Roofs near the Pacific Highway or the Mona Vale Road junction pick up road soot, while any shared system on the newer apartment buildings near the station is reached through the strata committee rather than one resident.
Many Pymble roofs have to work around trees for part of the day, and that makes the sunny hours more valuable. A clean panel is ready to use the light that is available when the sun clears the canopy, and that is one of the few things an owner can still influence once a system sits under a tree that has to stay.
Clean glass also gives you a truer reading of your system. If generation is still lower than you expected after a wash, the cause is less likely to be surface dirt, and you have a better basis for a conversation with your installer about shade or equipment.
Purified water with no detergent is what makes the method safe for the array. It dries spot-free and protects the glass and its coatings, and there is no chemical film left to hold the next round of dust and pollen. With a garden or bushland below the roofline, it is reassuring that only water is involved.
Getting onto a steep older roof is not a job for a homeowner. Team members are certified to work safely at heights and the work is fully insured, which is also what a strata manager will want confirmed before anyone accesses a common-property roof.
Before-and-after photos supplied with each clean show the state of panels you may never otherwise see. They also give you a dated reference to compare with your inverter's figures.
Council's Tree Assessment Guidelines say reducing bird or animal droppings is not a reason to prune or remove a tree, so an application on those grounds is unlikely to help. Having the panels cleaned is the simpler answer. Droppings are removed with purified water, leaving the glass clear and spot-free.
It could be either, and growth in the canopy is hard to judge from the ground. A clean takes soiling out of the equation, and the before-and-after photos show how much had built up. If figures stay low afterwards, your solar installer is the right person to check the system.
Access is assessed when quoting, including the roof pitch, height and how the array can be reached safely. Team members are certified to work at heights and the work is fully insured. Mention if the roof is an older slate or terracotta one, so it can be considered in advance.
Normally the owners corporation or strata manager, since a shared system and the roof beneath it are usually common property. They can call 1300 055 935 for a free quote. The before-and-after photos give the committee a straightforward record to pass on to owners after the work is finished.
How we clean arrays with purified water and no detergent, and why output recovers once the glass is clear.