Why your solar panels stop paying for themselves
Dust does not break a panel, it quietly takes a share of everything it makes. How to tell when yours need cleaning, and what never to do to them.
Nobody notices a dirty solar panel. There is no noise, nothing trips, nothing leaks. The bill just stops falling as far as it used to, and by the time you think to look up, the panels have been working at a fraction of what you paid for them for months.
Islamabad is a hard place for panels. There is construction dust most of the year, there are trees, and there are birds. Then the rains come, and instead of washing everything clean they turn the dust already up there into a film that dries hard and stays.
How to tell without climbing on the roof
Read your own inverter. It has a screen, and the screen knows. Look at what it is producing on a bright, cloudless day around noon, and write the number down. Do that once a month. You are not looking for a precise figure — you are looking for a number that keeps getting smaller while the weather keeps getting better.
That is a real measurement from your own system, which is worth more than anybody’s guess, including ours.
Then look from the ground. You can often see it. A panel that has gone matte instead of glassy, or has a pale tide-line along the bottom edge where water has run off and dried, is a panel losing you money.
What not to do
Never throw cold water on hot panels. This is the one that costs people money. Glass that has been in direct sun all afternoon and then gets a bucket of cold water thrown at it can crack from the shock. Clean early in the morning or in the evening, when the panels have not been baking.
Do not use dish soap or detergent. It leaves a film, the film attracts dust, and you are back where you started in a fortnight — only now with a sticky layer that is harder to shift.
Do not walk on them. Panels look solid and are not. The cracks you make are usually invisible and permanently reduce what the panel produces.
Leave the pressure washer alone. The seal around the edge of a panel is the one thing standing between the electronics and the weather, and a pressure washer is very good at finding it.
What a proper clean involves
Soft brushes, plenty of plain water, and somebody who does the frames and the gaps as well as the glass — dirt collects where the panel meets its frame and sits there holding moisture.
The other half of the job is looking while you are up there. Loose clamps, cable ties that have gone brittle in the sun, a junction box hanging off, a bird nest built underneath. None of that shows on the inverter until it is a problem.
How often
More often than people think, and it depends entirely on where you live. A house near a building site or an unpaved road needs it far more than one that is not.
The honest answer is to read the inverter, because your own system will tell you before anybody else can. When the noon figure on a clear day has drifted down and stayed down, it is time.