Why is my solar suddenly producing less power?

Nothing is faulty — the panels just can't see

It usually shows up the same way. The system that carried the house comfortably in October is struggling by January. The batteries are not reaching full. The inverter shows no error. Nothing tripped, nothing burned, nothing changed — except the output.

Before you call anybody, look at your panels.

A solar panel makes electricity from the light that reaches the cells through the glass. Anything sitting on that glass — dust, ash, bird droppings, a film of dried residue — is shade. It does not damage the panel. It just stands between the panel and the sun, and the output falls by roughly the amount of light being blocked. That is why the loss creeps in gradually and why nothing reports a fault: from the electronics' point of view, the sun is simply dimmer than it used to be.

The harmattan numbers

This is not a small effect, and in West Africa it is measured, not guessed.

• Field measurements in the region put harmattan soiling losses at 26–53% in the most affected locations — the top of that range is more than half the system's output gone to dust.
• Across the Sahara and sub-Saharan belt generally, dust accumulation costs 20–40% of production.
• At the peak of harmattan, the deposition rate is high enough that panels can need cleaning every two weeks to hold their output.

If your system seems to fade every December-to-February and recover after, this is almost certainly what you are looking at. The measurements are from MIT Media Lab's study of dust soiling on decentralised solar in West Africa, and a peer-reviewed review of dust and PV performance in Nigeria.

Rain is not a car wash

Here is the part that catches everybody, including people who have owned solar for years: waiting for the rainy season to clean your panels is not a maintenance plan.

Rain takes off the loose surface dust — the layer you can see move. What it leaves behind is a fine mineral film bonded to the glass. In urban areas — Lagos, Port Harcourt, Onitsha — traffic and industrial particulates mix with the rain into a residue that dries into a semi-permanent haze, and that haze alone can cost 15–30% of output. Worse, the light rain and dew at the start of the season can actually cement dust onto the glass before the heavier rains arrive.

So a panel that has "been rained on" is not a clean panel. It is a panel with a thinner, harder-to-see layer of shade — which is exactly why owners rule out dirt ("but it rained last week") and start suspecting the battery, the inverter, or the installer.

How to tell it's dirt and not a fault

You do not need to open anything, and you should not. Two checks tell you most of what you need to know:

1. Look at the glass — from the ground, or from wherever you can see the array without climbing. Visible dust film, dulled reflections, bird droppings, or streaking after rain all say soiling. If part of the array is shaded by something new — a water tank, a grown tree, a neighbour's extension — that is its own version of the same problem.
2. Compare output after a proper clean. If production comes back after the glass is cleaned, that was the whole story. If it does not come back, then call whoever installed the system — do not start opening boxes yourself.

Cleaning them safely

The cleaning itself is simple. The safety rules around it are not optional.

If the array is on a roof, the cleaning is a job for someone equipped to work at height. Do not climb onto a roof with a bucket, and never stand or lean on the panels themselves. Ask your installer whether panel cleaning is part of their maintenance visit — for most rooftop systems that is the right answer, and it pairs cleaning with the annual inspection the system should be getting anyway.

Where panels are genuinely reachable without leaving the ground — a low canopy, a ground mount:

• Clean early in the morning or late in the evening, when the glass is cool. Cold water on hot glass is a thermal shock the panel does not need.
• Soft brush, squeegee or microfibre, and plain water. The dirt is sitting on glass; it does not need force.
• No pressure washers, no abrasives, no scouring pads, no harsh detergents. These can damage the glass coating and the seals — and a scratch is permanent shade.
• Water and a soft tool touch only the glass. Cleaning is not an inspection: no wiring, no connectors, no opening anything, ever. Anything electrical is the installer's side of the line.

How often? During harmattan, every two weeks at the peak. The rest of the year, let the glass tell you — the check in the section above costs nothing and takes a minute.

If you are still choosing a system

Two things worth knowing before you buy, no brand attached:

• Some panels pick up light on the back as well, not just the front — off your roof surface.
• Some are built with frames designed to shed dust rather than collect it along the bottom edge — which in this country is not a small detail.

And ask the question almost nobody asks at the quoting stage: "how will these panels be cleaned?" An array laid out with cleaning access in mind, by an installer who offers the maintenance visit, will hold its output. "Zero maintenance" is not one of the honest answers — the numbers above are why.

The honest conclusion

A dusty system is a healthy system having a bad month. The output loss is real — measured past fifty per cent at harmattan's worst — but it is fully recoverable with water and a soft brush, on a schedule, done safely. Nothing needs replacing, and anyone who tells you otherwise before the glass has been cleaned is answering a question you did not ask.

That is the standard getsolar.ng holds anyway: you tell us about your house, an engineer designs around what you actually need, and the people who install it are the people who will tell you the truth about dust.