Why dirty panels make less power
Solar panels turn sunlight into electricity. Anything that sits on the glass, such as dust, smog residue, leaves or bird droppings, blocks part of that light. In many Pakistani cities a thin layer of dust builds up within days, especially in dry months and during smog season. You may notice the inverter showing lower output on a clear, sunny day. That is often the first sign that cleaning is due.
Bird droppings and leaves are worse than an even layer of dust, because they cover a few cells completely. One badly shaded cell can pull down the output of the whole panel, and sometimes the whole string.
How often to clean
- Dusty or smoggy cities (for example near main roads, factories or construction): roughly every 2 to 4 weeks.
- Cleaner areas: about every 1 to 2 months.
- After a dust storm or a long dry spell: clean soon, don't wait for the next round.
- In the rainy season, rain helps, but it often leaves a muddy film. Check the glass after the rain dries.
The safe way to clean
- Clean early in the morning or in the evening, when the glass is cool.
- Use a soft brush or sponge and plain clean water. A little mild soap is fine if the dirt is sticky.
- Never use detergent powder, acid, a hard brush or a pressure washer on the glass.
- Never pour cold water on hot panels in the afternoon: the sudden change can stress the glass.
- Don't stand or walk on the panels.
- Only go on the roof if it is safe. If the roof is high or slippery, call a mistri.
When to call a professional
Call a mistri if the roof is hard to reach, if you see cracked glass or burnt marks, or if output stays low even after cleaning. A good cleaner also looks at loose connectors and cables while on the roof, which you might miss.