One of the arguments for solar in the UK is that rainfall naturally keeps panels reasonably clean. This is partially true — but the UK climate also brings moss spores, lichen, bird nesting activity near panels, and autumn debris that rain alone does not resolve. A structured maintenance approach protects your investment.
How Often Should UK Solar Panels Be Cleaned?
For most UK installations, a professional clean once a year is the baseline recommendation. Properties in specific situations may need more frequent attention:
- Near trees: Clean twice per year (spring and autumn)
- Near farmland or building sites: Quarterly inspection; clean as needed
- Coastal properties: Inspect twice per year for salt deposition
- Low-pitch roofs (under 15 degrees): Twice per year — self-cleaning via rain is less effective at low angles
For standard pitched roofs in typical suburban locations, annual cleaning in spring (to clear winter debris and before peak generation season) is sufficient.
The Moss Problem
Moss is the UK solar panel's most persistent adversary. It thrives in the cool, damp conditions that characterise much of the British year, particularly in the north and west. Moss causes problems in two ways:
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- Direct shading: Moss build-up on the panel surface blocks light, reducing output
- Edge infiltration: Moss growth under panel frames traps moisture, potentially accelerating frame corrosion
Moss that has not yet taken hold can be removed with a soft brush and appropriate panel cleaning solution. Established moss requires professional treatment — specialist installers use biocidal treatments approved for use near solar panel surfaces and without abrasive tools that could scratch the glass.
Do not use pressure washers. High-pressure water can force moisture into panel connections, damage mounting seals, and void manufacturer warranties.
Bird Activity and Debris
In the UK, pigeons are the most common problem. Panels provide a sheltered, elevated nesting spot. The issues they cause:
- Droppings on panels: Localised but significant shading. Acidic droppings can also etch glass if left long-term
- Nesting material under panels: A fire hazard and an insulation trap for moisture
- Damaged cabling: Birds pecking at DC cables, particularly where rubber insulation is accessible
Anti-bird measures include mesh skirting fixed around the panel perimeter, which prevents access to the cavity beneath. These mesh kits are widely available from UK solar accessories suppliers and can be retrofitted to most mounting systems. Bird proofing typically costs £150–350 fitted by a professional.
Annual Maintenance Checklist
| Task | Frequency | DIY Possible? | Notes |
|---|---|---|---|
| Visual panel inspection (output monitoring) | Monthly via app | Yes | Flag any panel showing low output |
| Physical panel surface inspection | Annually | Yes (binoculars) | Check for soiling, moss, cracks |
| Professional panel clean | Annually (spring) | Not recommended | Use MCS-linked solar cleaning company |
| Bird mesh inspection | Annually | Yes | Check for gaps or dislodged sections |
| Inverter LED/display check | Monthly | Yes | Normal operation light should be solid |
| Inverter ventilation clearance | Annually | Yes | Clear any storage away from inverter |
| Roof penetration/flashing visual check | Annually | Yes | Look for lifted lead or cracked sealant |
| DC isolator switch check | Annually | Installer only | Confirm isolator operates freely |
| Cable management inspection | Annually | Installer only | Check clips, conduit, UV degradation |
| Generation vs. prediction review | Annually | Yes | Compare with MCS-predicted output |
Monitoring as a Maintenance Tool
Your inverter's monitoring app (mySolarEdge, GivEnergy Cloud, Sungrow iSolarCloud, or Enphase Enlighten) is your first line of maintenance defence. Set up generation alerts to notify you if daily output drops below a threshold for three or more consecutive clear days. This can indicate a fault before a physical inspection would reveal it.
When to Call a Professional
Call an MCS-certified solar engineer if you notice:
- A significant and sustained generation drop not explained by weather
- Inverter fault codes that persist after a restart
- Visible damage to panels (cracks, delamination, discolouration)
- Any sign of moisture in the inverter housing
- Burning smell near the inverter or DC cabling
