- solar panel cleaning
- rain does not clean solar panels
- Pretoria solar
- Highveld dust
- Waterkloof
Why Rain Does Not Clean Your Solar Panels
After heavy winter rain in Pretoria, we cleaned a Waterkloof home and the panels were still covered in dirt. Here’s why rain is not enough, and what actually works.
Izak vN
Operations Director & Founder
· 3 min read
Over the last few days Pretoria got a dose of winter rain. “Welcome” is a stretch: it was bitterly cold, and several of our scheduled cleans had to be postponed. On the first clear, sunny day that followed, we cleaned a beautiful home in Waterkloof.
What we found on the panels was a clear reminder of something many homeowners still believe: rain cleans solar panels.
It doesn’t.
The Car Analogy
Think about your car after a few days of rain. Does it come out sparkling clean?
Usually not. The rain may wash away some loose dust, but it often leaves behind water spots, dried mud, and a thin film of dirt. In many cases the car looks worse than before: streaky and dull.
Solar panels behave in much the same way.
What Actually Happens When It Rains
Rain can remove some of the lightest, loosest dust. But on the Highveld it rarely does a thorough job for several reasons:
- Dust mixes with water and turns into a light muddy film that sticks to the glass.
- Mineral content in the rainwater leaves spots as it evaporates.
- Bird droppings, pollen and heavier soiling are not dissolved by ordinary rainfall.
- Panel angle means water runs off quickly, without the scrubbing action needed to lift stuck dirt.
The result is often a panel that looks cleaner from the ground but is still coated in a fine layer of residue that reduces the amount of sunlight reaching the solar cells.
The Real Cost of That Film
On the Highveld, soiling regularly reduces solar output by 15–30%. Even after rain, a residual film can continue to block light and quietly cost the homeowner in lost generation, especially now that Tshwane electricity tariffs have risen.
That lost performance is real money on the monthly bill.
What We Saw in Waterkloof
After the recent rain, the panels on this Waterkloof home still carried a clear layer of dirt and spotting. The difference once we cleaned them with purified RO/DI water was immediately visible. The glass went from dull and filmed to clear and reflective.
This is something we see regularly across Pretoria and Gauteng, especially after light or moderate rain events.
Why Professional Cleaning Still Matters
Rain is free (if not always pleasant), but it is not a substitute for proper maintenance. A professional clean with purified water and soft brushes removes the film that rain leaves behind, restores output, and protects the long-term performance of the system.
Many of our customers now schedule regular cleans (quarterly or twice a year) so they are not relying on the weather to keep their investment performing.
Have your panels looked the same after rain?
If you’d like us to take a look or give you an indicative price, get in touch or use our instant price calculator.