Solar Panel Cleaning Frequency By Climate In Australia
In Australia one’s cleaning schedule for solar panels is a function of roof access, salt spray, rainfall, pollen, bird droppings and the like. For most homes here, once or twice a year will do; those with a tropical roof or in the dusty inland and along the coast may find they have to put in more effort.
There are no national rules of thumb to go by. The grime that accumulates on a leafy Tasmanian property is not the same as what you would see on a townhouse in Brisbane or a house in the Pilbara. Simon Redcliffe has put together this guide to tell you when to clean your panels in Australia and when to call in the pros, all without making an ordeal of roof maintenance.
A Quick Answer
If there is ash, dirt or bird droppings in plain sight, it is time to have them cleaned. Three to six months between inspections is the norm for the average household. Where the climate is arid or you are in a coastal suburb, quarterly cleaning will give a better return on the cost in terms of efficiency. An annual wash down might suffice in a rainy locale.
It is only when a film of grime covers several panels that cleaning becomes necessary. Some dust is not worth the ladder but if the buildup is heavy it will impede the light to the photovoltaic cells. The sensible thing is to keep an eye on performance from the ground and act on conditions as they are, especially with dust buildup on solar arrays.
Schedule to follow
| Australian setting | Starting frequency | What you will find | Time to step up |
|---|---|---|---|
| Arid and dusty inland | Every 3–6 months | Dust, red dirt, fine grit and ash | Following dry spells, earthworks or a dust storm |
| Coastal | Every 3–6 months | Bird droppings, dust, salt spray | After strong onshore winds, storms or a visible salt film |
| Tropical / subtropical | Every 3–6 months | Humidity, mould, pollen and bird droppings | Post wet season or extended humidity |
| Temperate / high-rainfall | Every 6–12 months | General dust, leaves, pollen | When rain has not done its job |
Do not take these as any kind of guarantee. The tilt of the panel, roof shading and water quality can alter things. Put your inverter or app to the test before and after, though cloud cover and electricity use at home will put their own spin on the figures.
How climate dictates the work
Rain does not equate to a pressure washer. It is true that a hard downpour can rinse away loose dirt yet it will not budge salt deposits or sticky pollen. Lighter showers tend to push dust to the bottom of the panel and leave mineral marks. So a bit of cleaning after the rain has passed and the panels are dry is often called for. Have a look at the Bureau of Meteorology for official data on local rainfall and seasonal dryness.
Weather And Roof Position
Then there is the matter of the roof itself. A panel with some tilt will shed water and dirt better than one that is almost flat. Under trees or in the shade of a low-pitched roof the glass will stay damp and grime will hold on.
Access is also a factor. A professional can make short work of a single-storey home with good ground access but a steep two-storey roof off a narrow driveway is another story and will demand the right safety gear. The number of panels is beside the point; it is the access that drives the time and expense.
More care required in arid regions
You will encounter long dry runs in the Northern Territory, Western and South Australia and in parts of Queensland and New South Wales. Unsealed roads and mining or farming activity mean dust settles in a hurry. In the Pilbara or the Red Centre a morning can be clear and then a wind in the afternoon brings on a fine red-dust issue.
Three monthly inspections are in order in such climates, with two to four cleanings a year. Do not hesitate to do more in the wake of bushfire smoke, construction or a dust storm. The trouble with bushfire ash is that it will not just be carried off by the wind; in the presence of moisture it can put down a film.
Prevent Scratches And Grit
It is best to give the glass a rinse with some water before you do anything else, as fine grit will do to the surface what sandpaper does if you try and scrub dry dust from it. A soft brush or whatever method the manufacturer vouches for will do. Leave abrasive pads, pressure washers and strong detergents alone unless you have the panel maker’s say so.
There is an error people are prone to make again and again: they will set about cleaning on a hot day. The glass is then hot and the work is uncomfortable, if not risky, and the water has a way of evaporating into spots. Make it early morning or late afternoon, assuming the roof is dry underfoot and there is no storm about.
Salt Is An Issue For Coastal Homes
Panels out on the coast have to contend with humidity, salt spray, sand in the air and the likes of seabird droppings. Rain is not always sufficient to clear the hazy film left by salt, and without proper inspection one can see coastal corrosion set in on the mounting hardware.
A quarterly check and two cleanings a year should suffice for most coastal properties. Those on a headland or a windy beach where the ocean spray is direct may find they have to put in the time every three or four months. Inland by a few kilometres and the local dust and wind dictate how often attention is required.
Get The Salt Off Before It Dries In
Under a strong sun salt residue will bake and be all the more difficult to dislodge. If there are dull patches or a white film, do not put it off till the next good rain. Have a professional come round to inspect any exposed rails and clamps while he is at it.
Then again, do not think of it as electrical maintenance. That is for mending loose mounts or cabling; cleaning is only for surface contamination. Should a panel look to have moved or you spot wiring and cracked glass, stay off the roof and put in a call to a solar professional.
Wet Tropics Call For Seasonal Inspections
Much of Queensland and northern Western Australia are tropical or subtropical and have a wet season to match the heavy rainfall, humidity and sunlight. The rains will run off the odd bit of dust but pollen and bird droppings and other organic matter will remain.
An inspection is in order either side of the wet season and a clean when the panels are still dirty. Most in the tropics will do it three or four times over the year, perhaps more if the roof is in the shade of trees. From November through April the cyclone alerts should be taken as your cue to hold off on any roof work in bad weather and have a visual check of the system in the aftermath of a severe storm.
Make Allowance For The Wet
When the weather has broken, a calm and dry morning is preferable to climbing up while the roof is slick and there is a storm watch in force. In the Top End one would be unwise to regard the tail end of a downpour as an open invitation. Sudden storms and mossy tiles do not mix well.
After a cyclone it is better to stand on the ground and note any fallen branches or frames that have come loose. Do not lay hands on damaged equipment. You will get more from a professional than a stint on the ladder and it is less likely to result in an emergency room visit.
Temperate Climates Will Tolerate Longer Intervals
In Victoria, Tasmania, parts of southern New South Wales and Western and South Australia, rainfall tends to see to the loose dust. But isolated dirty patches can come from leaves, chimney residue and bird droppings.
Put in an inspection half yearly and plan to clean once or twice. A property in Hobart or leafy Melbourne might demand more of you than an unsheltered one, come the spring pollen or autumn leaves. The rain will lessen the need for a routine clean but it will not get rid of everything.
Do Not Rely On The Rain
It is a common misconception that a rain shower will put performance back where it should be. The lower edge of the panel or a film of dust and bird droppings may be right where they were. If the panels are looking patchy, have a look at the inverter output in similar conditions to see if it is worth the effort.
One cannot take a cloudy day and a sunny one and claim a miracle of cleaning. With inverter limits, temperature and household demand the output will vary. Judge it on a pattern of several days.
Signs Your Panels Need Cleaning
There is no better indicator than grime you can see with your own eyes, though a change in performance will tell you as much. When you have obvious contamination to go along with an output that does not measure up under the same weather conditions, the argument for a clean is made.
I have found at my cottage in Melbourne that the panel which looks the worst is not necessarily the one giving you trouble. A bird dropping stands out more than a fine film over the array, and tree shade has a greater effect on both. Do not put down every kilowatt-hour you are short on dust; take a good look at the system first.
- Look for a steady layer of dust, mud streaks, pollen or leaves, white salt marks and the like.
- See if the numbers have dropped in comparable sunny spells with no new inverter or shading problems to account for it.
- Make an inspection after any storm damage, bushfire ash, strong winds or protracted dry weather, or if there has been construction in the vicinity.
- If the roof is high, steep, slippery or in the way, leave the cleaning to a professional.
Expectation Versus Reality
You might think a good clean puts an end to dust issues for good. In reality, the moment the wind, birds and traffic make their presence felt the panels will be dirty again. It is maintenance, not some kind of parlor trick, and lessened output could well be due to shading or equipment. Should the output be anything but good once you have finished, get the system looked at. There is no one solution for a bad inverter, wiring damage or degrading panels. And a cleaner who will not trouble to inspect the site and know the baseline should not be putting forward figures on how much he can improve things.
Clean Panels Without The Roof Drama
Shine is secondary to safety. A roof covered in water or detergent is no place to be, and the panels are making electricity as long as there is light on them. If you cannot get to them from the ground or a secure work area in all safety, call in the professionals.
Where the job is low risk and from the ground, use a soft brush and clean water and do not walk on the panels; follow what the manufacturer says and pick a time when it is cool and calm. Hard water will put mineral spots on the glass so the quality of the water is important; a service provider with deionised water will give you a better finish.
A Simple Cleaning Checklist
- Put off the task if the forecast calls for wet or windy conditions, a storm or excessive heat.
- From the ground check for hazards on the roof, any cabling showing, loose panels or cracked glass.
- Only switch off equipment as the maker instructs, keep your hands off electrical components.
- Rinse away the loose dust before applying a soft brush and some suitable clean water, nothing abrasive.
- Let the panels dry and then put the system output to the test in like weather to see if any film is left.
Costs for a professional clean will differ across Australia depending on how many panels there are, the height of the roof, the state of the roof and how far they have to travel. An easy single-storey will not set you back as much as a remote multi-storey with a steep pitch. Get a written quote and make sure it covers access, rinsing, travel and any checks on the equipment.
The Right Maintenance Plan
Keep it straightforward: a three to six monthly inspection and a clean when you see the need or the performance is on the slide, then let your climate dictate the interval. You will find arid, coastal and tropical homes demand more of your attention than a temperate property in a sheltered spot.
Simon Redcliffe would have you treat the panels as you would any other part of the house that has a job to do: be guided by the evidence and the weather, do not put yourself on a roof to be penny wise over a service fee. Safe access and a bit of common sense in monitoring are as important as a clean array for your solar energy output.
Frequently Asked Questions
Homeowners in Australia tend to ask these before they book in a cleaner or put on the hose. What follows are short answers of a practical nature.
How often in Australia?
Once or twice a year to start with, then you can adjust. Every three to six months for those in arid or tropical climes, say, or perhaps every six to twelve for a home in a temperate zone.
Will rain do the job?
Not of itself. It will wash off the loose dust but you will still have your salt residue, mineral marks and so on. Better to have a look after it has rained than to assume the panels are clean.
Is dust going to affect performance?
It can, a thick layer will rob the cells of light. Then again, a faulty inverter or some cloud cover and you will see the output fall.
When is the best time?
Early in the morning or late afternoon, when the glass is not so hot and the water does not evaporate right away. Pick a dry and calm day, never a wet one.
Make a professional of it?
If you do not have the experience or gear for working on a roof it is the sensible option. Equally so if the panels are hard to get to or the roof is steep and laced with salt or ash.
