Solar Panel Cleaning: Do You Actually Need to Do It?

You've had your panels installed, they're generating nicely, and then you get a flyer through the door offering solar panel cleaning for £150. Is it worth it? The short answer: usually no, sometimes yes.

What the research says

Studies across the UK and Europe consistently show that rain does a remarkably good job of keeping panels clean. In most of England, Scotland, and Wales, the output difference between cleaned and uncleaned panels is 1-3% annually. On a system saving £900/year, that's £9-27 in lost generation. Not worth paying £150 to recover.

The exception is if your panels are:

• Under trees: Bird droppings and tree sap don't wash off easily. A panel covered in bird mess can lose 15-25% of its output in that area.
• Near a busy road or construction: Dust and particulates build up faster than rain can clear.


• At a very shallow angle: Panels below 15 degrees don't self-clean as effectively because water pools instead of running off.


• In agricultural areas: Pollen, dust from harvesting, and agricultural sprays can coat panels.

If you do need to clean them

DIY approach: A garden hose from ground level is usually sufficient. Use plain water - no detergent, no pressure washer. Do it in the morning or evening when panels are cool (cold water on hot glass can cause microcracks). Never walk on your roof to clean panels. The safety risk isn't worth it for a few percent of output.

Professional cleaning: If your panels are inaccessible or heavily soiled, professional cleaning typically costs £4-8 per panel (£50-100 for a typical system). Once a year is plenty for most situations. Twice if you're under trees.

What actually affects output more

Rather than worrying about cleaning, these factors have a bigger impact on your system's long-term performance:

• Inverter health: Check your monitoring app regularly. A failing inverter can cut output by 50-100%. This matters far more than a bit of dust.
• Shading changes: Has a neighbour's tree grown since installation? New shading is the most common cause of unexplained output drops.


• Wiring issues: Loose connections develop over time, particularly at junction boxes on the roof. An annual visual check is worthwhile.

For the vast majority of UK homeowners, solar panels are genuinely low maintenance. Rain keeps them clean, there are no moving parts, and modern equipment is built to last 25+ years. If you're considering installation and worried about upkeep, don't be - it's one of the simplest home investments you can make.

Our solar savings calculator already accounts for typical soiling losses in its projections, so the figures you see there are realistic.