Solar panel maintenance

A photovoltaic system has almost no moving parts, so its mechanical wear is minimal compared with other ways of generating energy. Most of the 'maintenance' comes down to keeping the panels clean and periodically checking that everything is working properly.

That does not mean it is 'install and forget': basic care protects output and extends the service life of an investment designed for 25 years.

It is worth being clear about what is being protected. It is not just generation: it is also the watertightness of the roof where the structure was anchored, the integrity of wiring exposed to the elements under a tropical sun, and the electrical safety of an installation working at considerable direct-current voltages. Those three fronts are what justify a periodic inspection even when output looks fine.

Dust, leaves or bird droppings reduce output by blocking light. In areas with regular rain, that handles much of the cleaning; in dry or dusty areas it is worth cleaning more often.

There is a nuance that surprises people: uniform dirt takes off little, but concentrated dirt takes off a lot. A thin layer of dust spread over the whole panel reduces output proportionally and modestly. A bird dropping or a stuck leaf, by contrast, completely blocks a cell, and that cell can drag down its whole group. So removing four specific spots is worth more than thoroughly washing an evenly dusty panel.

Cleaning is done with water and soft implements, without abrasive products that could scratch the glass, and with care at height. It is best done early in the morning or late in the afternoon: throwing cold water on a very hot panel subjects the glass to unnecessary thermal shock, and the water evaporates before it can carry the dirt away.

If the water in your area is very hard, dry the panels or use low-mineral water: the limescale deposits left behind as it evaporates can end up blocking more light than the dust you removed.

For safety, many owners contract cleaning as part of a maintenance plan rather than doing it themselves on the roof. That is a reasonable decision: most accidents associated with solar installations are not electrical, they are falls.

There is no universal frequency. It depends above all on how much dirt your roof receives and on whether rain washes it off.

In areas with frequent rain and enough tilt for water to run off, nature does almost all the work and occasional checks are enough. In dry or dusty areas, near unpaved roads, building sites or crops with soil work, the frequency rises noticeably. Near the sea, salt adds to the dust. And if there are trees nearby or birds that use the roof as a perch, the determining factor stops being the calendar and becomes inspection.

The best guide is not the calendar but the data: if monitoring shows output falling relative to comparable earlier days and the weather does not explain it, it is time to look at the panels. That approach avoids both over-cleaning and losing months of generation without noticing.

An annual system inspection checks the condition of the wiring, the connections, the mounting structure and the operation of the inverter. It is a job for a technician, not the owner, because it involves handling a live electrical installation and working at height.

Much of what it checks is not visible from the ground and does not appear in the monitoring app, and that is where its value lies.

System monitoring — the app or platform showing generation — is your best ally between inspections: a sustained drop in output is usually the first sign that something needs attention.

For it to be useful you have to know how to read it. Output varies enormously from one day to the next because of cloud cover, so comparing Tuesday with Monday says nothing. What does tell you something is comparing long periods — this month against the same month last year — or looking at the shape of the daily curve. A clean bell-shaped curve indicates normality; notches or steps at the same time every day give away shading; a prolonged flat top can indicate the inverter is clipping.

Two minutes a month is enough. Many systems let you set up automatic alerts for a drop in output or an inverter fault, and switching them on is the cheapest way of not finding out too late.

Panels usually carry performance warranties of 25 years or more and keep working after that, with a slight annual loss of capacity. They do not stop producing all at once: they age slowly.

The inverter has a typical service life of 10 to 15 years, so it is usually the only significant replacement during the life of the system. It is worth budgeting for it from the start as part of the total cost of the installation, not as an unforeseen expense. It is also the most exposed component: if it is outdoors or somewhere unventilated and very hot, its life is shortened.

The mounting structure should last the whole life of the system if the right material was chosen for the environment. In a salt-laden environment, that 'if' matters.

If your installation has batteries, they have their own service life, clearly shorter than the panels', and will also have to be replaced at some point.

All panels lose capacity over the years. It is an expected phenomenon, not a defect, and it is covered by the performance warranty.

The usual pattern is a somewhat larger drop during the first year of exposure and, from then on, annual degradation on the order of half a percentage point. At that rate, a panel retains around 85-90% of its original capacity after two decades, which is exactly what manufacturers guarantee.

What is not normal is an abrupt drop, a sudden step in output or a loss well beyond the guaranteed curve. That points to a specific fault — a damaged panel, a deteriorated connector, a disconnected string — and not to ageing. The difference between degradation and a fault is in the shape of the curve: degradation is slow and gradual, a fault is a step.

Watch for a few signs that indicate it is time to call the technician. None of them requires you to climb onto the roof to check.

Some well-intentioned practices do more damage than the dirt they are trying to remove, and others are outright dangerous.

Many installers offer annual plans. Before signing one, it is worth knowing what is in and what is not, because very different scopes are sold under the same name.

A reasonable plan includes at least one annual visit with an electrical and mechanical inspection, cleaning of the panels, a report on the state of the system and a review of the inverter's alarm log. More complete plans add priority attention in the event of faults, handling of warranty claims with the manufacturer and a set number of corrective visits.

Ask specifically who covers the labour if a piece of equipment has to be replaced under warranty, because the manufacturer's warranty usually covers the equipment but not the work of replacing it. That difference can be considerable on an installation at height.