A skylight cleaning robot can work alongside rooftop PV, but the two systems fight over the same space in 2026. The main risks are cable snag on panel edges, water spray onto live junction boxes, and shadows cast on cells during a slow pass.
Roofs that mix skylights and solar are common now. The glazing lets light in, the panels turn the rest into power, and both need cleaning. The mistake is treating them as one job with one method.
Why can’t the robot just drive over the panels?
Because PV glass is not structural in the way skylight glazing is. Modules are designed to take snow load distributed across the frame, not a 20-30 kg tracked machine landing on one corner. A robot crossing a panel can micro-crack cells, and micro-cracks do not show up in output until months later. Keep the machine on the walkable glass and the service lanes.
Is DC cable snag a real hazard?
Yes. String cables and connectors run along panel edges and across the roof. A tracked machine rolling over a loose DC lead can either damage the cable or stall and shear a connector. On a live string, a damaged connector is an arc risk. Before any robot pass, do a cable sweep and tie down anything loose within about 300 mm of the machine route.
- Sweep and tie DC leads before every pass.
- Keep water spray at least 1 m from junction boxes.
- Never clean a panel row with a wet machine while the inverter is in fault.
- Route the robot across dry service lanes, not over cell surfaces.
Does water spray damage the panels?
Rain falls on panels constantly, so ordinary water is not the problem. The problem is pressurised spray forced into sealed connectors and junction boxes, which are water-resistant, not waterproof. A spray bar at 3 bar aimed at an MC4 connector can push water past the seal. On hybrid roofs, run the robot on a damp-pad setting and keep the spray bar pointed away from anything electrical.
Do robot shadows cut panel output?
Only while it is passing, and briefly. A shadow across one cell in a string can drop the whole string’s output by a meaningful margin during that moment, but the effect lasts seconds per panel as the machine moves. It does not justify buying a separate cleaner, but it does mean you should clean the glass when generation is low, early morning or evening, rather than at peak sun.
Who should separate the two jobs?
If more than 30 percent of the roof is PV, run two separate methods and two separate crews. Robots for the glazing, a dedicated dry-brush setup for the panels. Mixing them invites slips, snags and cable damage. If the roof is mostly glass with one small array, one operator can do both in sequence with a cable sweep between.
The practical rule: clean glass first while the roof is dry, then do a cable-aware pass near the array. Our notes on solar and glass hybrid roofs go deeper on sequencing.
What about the frames and mounting rails?
Between the skylight glass and the PV array there is usually a run of mounting rail, clamped feet and flashing. A robot crossing that zone risks catching a clamp bolt with a track. Walk the boundary before the first pass and mark any bolt head standing proud of the rail. A 15-minute survey saves a stalled machine and a bent track.
Watch the flashing lap at the low edge too. That is where the robot, working downhill, is most likely to bump a loose edge strip. On wet glass, the track can slip on the metal and scar the coating, so keep the machine on the glazing and finish the flashing by hand.
How should the two jobs be sequenced?
Do the glazing first, in the cool of the morning, then sweep cables and clean the panels once the roof is dry. If the panels are dusty, a dry brush first keeps mud off the glass; if the glass is the priority, the reverse order works better. Never run both in one continuous loop, because the transition is where mistakes happen.
What certifications matter near PV?
Look for IP-rated machine housings and a documented method statement covering electrical proximity. Many insurers also ask for a cable-inspection record before any work on a live roof. It is the same paperwork discipline that a CE-marked machine and a trained operator already imply, but on a PV roof the inspector will actually read it.
Can one operator cover both systems?
On a mostly-glass roof with a small array, yes. One trained operator can run the robot on the glazing and then do a dry-brush pass on the panels, provided the cable sweep and the spray discipline are followed. The risk is fatigue and shortcuts late in the shift, so keep the electrical pass early, while attention is high, and leave the plain glazing for later.
On a PV-heavy roof, split the roles. Mixing them invites a machine onto a live panel or water near a junction box, and neither mistake is worth the saved labour. Two people, two methods.
Key Takeaways
- Never drive a 20-30 kg robot over PV glass; micro-cracks appear months later.
- Tie down DC leads within 300 mm of the machine route before every pass.
- Keep spray at least 1 m from junction boxes; sealed is not waterproof.
- Robot shadows briefly cut string output, so clean at low generation hours.
- If PV covers over 30 percent of the roof, split the work into two methods.