Here is a question that comes up online all the time. Someone has just had solar fitted, they look up at the roof, and they spot a faint mark on one of the panels. Straight away the worry sets in. Is it a fault? Is the panel going to fail?
Then come the replies. People who have never seen the system pile in: get your installer back, that is a shoddy job, that panel will fail, terrible work. None of it true, all of it loud. So let me set the record straight on what these marks actually are and why, in almost every case, there is nothing to worry about.
What the marks usually are
I went out to look at a system where the owner had spotted this. The marks people get alarmed about are tiny. Often they are minuscule, barely there at all. Sometimes they are bigger, about the size of a palm print.
And there is a good reason they are the size of a palm print. They are a palm print.
We handle these panels with gloves on. But if a glove rips, or someone has something on their hands, or a panel is moved without gloves for a moment, you can leave a faint oily mark from the skin. It transfers onto the glass like a fingerprint on a window. That is all it is.
Why it does no harm at all
A greasy mark on the glass has no effect on how the panel works. None. The panel underneath is completely fine. It is not a crack, not a flaw in the cells, not a sign of a bad install. It is grease sitting on the surface of toughened glass.
You will not see it from the ground. From a few metres away on a roof, a palm print on glass simply disappears. It does not reduce your generation in any way you would ever notice or measure.
The rain will deal with it
Here is the best part. You do not need to do anything about it.
These panels live outdoors, fully exposed to the weather, and it rains plenty in this country. Rain washes a greasy mark off the glass over time, and usually not much time at that. Within a few weeks of normal British weather it will be gone on its own. The system is designed to be self cleaning to a large degree, which is exactly why we do not clamber about cleaning panels as a routine.
Why we will not clean it off for you
Some people understandably say: “I have paid a lot of money for these, can you just clean the mark off?” Our answer is no, and I want to explain why, because it is not laziness. It is care.
We do not know exactly what coating is on the glass of any given panel. It might be plain glass with no coating. But many panels carry an anti reflective coating, and that is the issue.
An anti reflective coating is a very thin layer on the glass that cuts the amount of sunlight bouncing off the surface. Less reflection means more light reaches the cells, which means more electricity. It is a genuine benefit, and it is delicate.
If we start scrubbing at the glass with cleaners or cloths, we risk damaging or removing that coating. That would do real, lasting harm to the panel, far worse than a temporary smudge that rain will remove for free. So the safe choice, the choice that protects your investment, is to leave it alone.
A quick word on cleaning in general
While we are here, it is worth knowing how to think about cleaning panels at all.
- Most domestic systems do not need regular cleaning. Rain does the bulk of the work.
- If you ever do have panels cleaned, use a specialist who understands solar glass, plain water and the right equipment, and who will not use harsh chemicals or abrasive pads.
- Never let someone go at your panels with a jet wash or a kitchen scourer. That is how coatings and seals get damaged.
- We do not clean panels off ladders, and neither should anyone else. Working at height needs proper access.
In short, the gentlest approach is almost always the right one, and most of the time the right approach is to do nothing.
Do not let the internet panic you
The wider point here is about the noise online. A faint mark on a new panel becomes, in the comments, a failing system and a cowboy installer. It is rarely either. Most of these posts are people reacting to something they have never seen, with confidence they have not earned.
If you genuinely have a concern about your system, the answer is not a stranger online. It is the company that fitted it. A proper installer will come and look, tell you straight whether it matters, and explain why. A faint palm print does not matter. We are happy to say so.
The bottom line
A mark on your new solar panels is almost always a harmless handprint from installation. It does not affect performance, it is invisible from the ground, and the rain will wash it away within a few weeks. We will not clean it off, because scrubbing risks the anti reflective coating, and that would do far more harm than the mark itself.
We install solar and battery systems properly across Cambridgeshire, Bedfordshire and Northamptonshire, around Huntingdon, St Ives, St Neots, Buckden and the surrounding villages. If you have a question about your system, real or imagined, call the office on 01480 400607 or request a survey through our website.
Jason Pope
Owner, Selec Group