Before you go...
We built a free scorecard that shows how your heat pump, ventilation and solar systems are performing. Results are usually surprising.
Get my score
No thanks
We built a free scorecard that shows how your heat pump, ventilation and solar systems are performing. Results are usually surprising.
No thanksWe built a free scorecard that shows how your heat pump, ventilation and solar systems are performing. Results are usually surprising.
No thanks
You've had your solar panels for a year or so. The app ticks along. Power's being generated. And at some point, you've probably wondered: do these things actually need anything done to them, or do they just keep working?
It's a reasonable question. The installer handed over the system and left. Nobody gave you a maintenance schedule. When you search online, you get "solar panels are basically self-maintaining" sitting right next to "get them professionally cleaned every six months." The gap between those two positions is where a lot of NZ homeowners get stuck.
This is what a professional solar panel service actually involves, what you receive at the end of it, and how to work out whether your specific installation needs regular professional care.
A thorough service should follow these steps:
Before anything gets touched, the technician does a visual inspection of the entire array. They're looking for cracked glass, wiring issues, frame damage, corrosion, bird nests, or debris that could affect drainage. This baseline matters. You need to know what you're starting with.
The cleaning uses soft-bristle brushes or microfibre cloths with purified or deionised water where appropriate. Auckland's water supply is relatively soft, so mineral residue from tap water is modest, a proper squeegee finish largely addresses it. The technician applies gentle pressure only. High-pressure washing damages seals and the glass surface.
The process removes dirt, dust, bird droppings, lichen, pollen, and organic growth. On NZ installations, lichen deserves specific attention. Auckland's humidity creates conditions where lichen bonds chemically to the glass. Rain won't remove it. Specialist cleaning solutions are required. For a full explanation of what lichen does to panel glass and why it requires a different approach from standard cleaning, see lichen, moss, and biological growth on solar panels.
While cleaning is underway, the technician also inspects frames and mounting hardware for corrosion, loose fittings, warping, or damage. Gutters and drainage areas around the panel array get cleared of debris.
Before cleaning begins, the technician takes an inverter output reading to establish a baseline. After the clean is complete, a second reading confirms what the service actually recovered. Without both readings, there is no objective record of whether the work made a difference.
The visit ends with a written condition report: before and after photos, a record of what was found, documentation of what was done, and any issues flagged for follow-up. For a full breakdown of what a condition report should cover component by component, see what a proper solar panel condition report should include.
A professional solar service does not include electrical repairs or structural work. If the inspection turns up a faulty inverter, damaged wiring, or a structural problem with the mounting, a good technician will document it and refer you to a qualified electrician or your original installer.
For a specialist service in Auckland that includes inspection, cleaning, before and after inverter readings, and a written condition report, expect to pay between $249 and $615 for a standard residential system.
The main factors that move the price are the number of panels, roof height and access difficulty, the level of contamination on arrival, and whether the roof is flat or low-pitch. Flat or low-angle installations require more involved cleaning because water pools at the lower panel edge rather than draining away.
At the lower end of the market, some operators charge a per-panel rate with no inspection and no condition report. The price is lower because the scope is narrower. Before booking a service quoted well below this range, ask what it actually includes.
A few things worth checking before you book.
No pressure washers. A professional service uses soft-bristle brushes and low-pressure water only. High-pressure washing forces water into electrical components and can destroy panel seals. Any operator using a pressure washer on solar panels is doing the job incorrectly, and your warranty may not cover the outcome.
Purified or deionised water. Ask directly whether they use purified water. It dries without leaving mineral residue on the panel glass. In Auckland's relatively soft water supply the practical difference for general cleaning is modest, but it remains a baseline indicator of a specialist service rather than a general exterior cleaner who added panels to their list.
A written condition report with before and after photos. If this is not included as standard, ask why. It is a basic professional requirement, not an optional extra. Without it, you have no maintenance record and no baseline for the next visit.
Before and after inverter readings. This is the only objective measure of what the service recovered. Without those readings, output improvement is invisible. You are taking the technician's word for it.
For homes on tank water. If lichen treatment involves biocides, confirm that the chemicals used carry AS/NZS 4020 certification — the standard for materials safe in contact with drinking water — and that a disconnect-and-flush protocol is followed before any application. Most homeowners on rural or semi-rural tank water do not think to ask this. It is worth asking.
One to two hours on site, depending on array size and how dirty the panels are. A small residential array in reasonable condition takes less time than a larger system with significant lichen or heavy bird activity.
You can clean your own panels if you do it correctly. Soft brush, gentle water flow, no harsh chemicals. It's similar to washing a car properly.
The practical limits are real though. Tap water leaves mineral spots. Safe rooftop access requires the right equipment. And most people who clean their own panels won't also inspect frames, check mounting hardware, or verify that performance actually improved after cleaning. Those inspection steps are where the real value sits in a professional service.
Not every installation needs the same service interval. The right frequency depends on your specific environment. Flat or low-pitched roofs, coastal properties, homes with significant bird activity, and areas with trees close to the roof all accumulate contamination faster than steeply pitched inland installations. Auckland's humidity also means lichen is a realistic risk across a wider range of suburbs than many homeowners expect. For a full guide to what determines your maintenance frequency and how to build the right plan for your system, see solar panel maintenance in NZ: how to build the right plan.
Anything under 10 degrees doesn't self-clean. Rain runs off too slowly to carry debris away. Light rain leaves dust as dried mud rather than washing it. Accumulation on flat-roof systems is inevitable, not a possibility.
Bird droppings cause significant localised output loss. They create hotspots over the cells they cover, are acidic, and bond to the glass, rain does not shift them. Dust reduces output gradually across the array. Droppings reduce it fast from a concentrated point.
Seasonal pollen, sap, and leaf debris land on your panels and build up on the glass surface. Rain does not reliably remove them, particularly pollen, which combines with moisture to form a film that bonds to the glass. NZ homes commonly sit close to trees and hedging, and pollen does not respect property boundaries — neighbouring vegetation contributes as much as your own. Spring and autumn are the worst periods.
Within roughly a kilometre of the ocean, salt spray accumulates on the glass and blocks light. It also accelerates corrosion of frames and mounting hardware. If metal fixtures around your home; railings, outdoor fittings, air conditioning units, rust faster than you'd expect, your panels are in the same environment.
Fine particles from cement and building materials accumulate faster than natural dust and are harder for rain to shift. If there's been active building work within a few hundred metres in the past 12 months, it's worth checking your panels.
Lichen growth happens across a wide range of suburbs, not just coastal or heavily vegetated areas. Auckland's high rainfall and persistent winter humidity create the specific conditions that drive biological growth on panel glass. For a full picture of how Auckland's climate affects biological growth on solar panels, the detail is covered there. If your panels haven't been cleaned since installation and you're in Auckland, lichen is worth checking for.
Your monitoring app or inverter display is the first place to look. If output is noticeably lower than the same period last year and the weather pattern hasn't changed significantly, contamination is a likely cause.
From the ground, using your phone camera with zoom, you can often see white streaking from bird droppings, a visible film, or greenish patches from lichen. Significant visible contamination at ground level usually means measurable output loss.
Check the pitch of your roof visually. If your panels sit nearly flat or on a low-slope roof, rain self-cleaning won't be effective.
Look at what's around the roof. Trees that drop leaves or pollen onto your car are dropping the same material onto your panels. Nearby construction in the past year is worth noting.
General soiling from dust and pollen causes modest output losses in Auckland's high-rainfall climate. The IEA estimates global average soiling losses at 3 to 5 percent annually, and NZ conditions typically sit at the lower end of that range. Panels with established lichen or concentrated bird droppings lose significantly more from the affected cells, the loss from those deposits is not proportional to how much of the panel they cover.
The loss is gradual and invisible. Your system still produces power. The monitoring app still shows numbers. The drop only becomes visible when you compare against expected output or a previous clean baseline.
Start with the Home Energy Health Assessment. It takes around three minutes and gives you a clear picture of where your systems stand. If professional solar cleaning is warranted, you'll know. If it's not, you'll know that too.
For most NZ installations, once every one to two years is a reasonable starting point. How often your specific system needs cleaning depends on your environment. Flat roofs, coastal locations, properties with nearby trees, and areas with significant bird activity all accumulate contamination faster than steeply pitched roofs in low-risk locations. Your monitoring app is a reliable guide. If output drops noticeably compared to the same period last year, contamination is a likely cause.
Rain helps on steeply pitched roofs with consistent rainfall and light contamination. It doesn't reliably clean flat or low-angle installations, where water runs off too slowly to carry debris away. It also won't remove lichen, which bonds chemically to the glass and requires specialist cleaning solutions. Bird droppings and tree sap are similarly resistant to rain. If you're relying on rain to maintain your panels, check whether your roof pitch actually supports that. Many NZ installations don't.
DIY cleaning with a soft brush, gentle water flow, and no harsh chemicals is valid for light maintenance on accessible, low-risk installations. The main limitations are rooftop access requiring proper safety equipment and the absence of any inspection component. A professional service includes an inspection before cleaning begins, cleaning with purified water, before and after inverter readings to confirm what the service recovered, and a written condition report with photos. For installations in higher-risk environments, the inspection component is where the real value sits.
Dirty panels reduce output rather than causing immediate damage in most cases. Bird droppings are an exception; they're acidic and can degrade the glass surface if left long-term. Lichen, if left to establish and spread, can also cause surface damage over time. The more common consequence of neglected panels is gradual, invisible output loss. The system still runs. It just generates less than it should.
A condition report from a professional solar service should include before and after photos, a record of the contamination found, documentation of the cleaning carried out, and details of any issues identified during the inspection; frame corrosion, loose mounting hardware, wiring concerns. Anything outside the scope of a cleaning service should be documented clearly and referred to the appropriate specialist. A written condition report is a basic professional standard, not an optional extra.
That depends on your installation. For systems in low-risk environments (steeply pitched roofs, consistent rainfall, no nearby trees or significant bird activity), the case for frequent professional cleaning is less clear. For installations on flat roofs, coastal properties, or areas with trees, construction, or high bird activity, the output recovered from a professional clean typically exceeds the cost of the service.