Solar panel cleaning robots fail when builders underestimate fall risk. A panel is a slippery tilted glass surface; suction alone is a bad primary attachment. For DIY, the safest design is rail-guided or edge-guided: the robot references the panel frame and cannot drive off the array.
The cleaner itself is simple: a microfiber roller or wide pad, a small mist pump, and two geared drive wheels. Avoid pressure washing; panels need gentle cleaning, not force. The robot should move slowly across the panel, return to the same edge, and be removable by hand.
For a single home array, the goal is not full industrial autonomy. It is a tool that keeps you off the roof edge and gives repeatable cleaning passes. Use a tether while testing, even if the robot has edge sensors.