Most plug-in solar kit guides focus on the panels and the microinverter. The cable run from the panels to the indoor socket gets less attention, but getting it right affects both safety and how professional the installation looks. Here is how to handle it for the three most common scenarios.
Balcony installation: through the door or window
The most common cable route for a balcony installation is through the gap at the bottom of a patio door or sliding door, or through an adjacent window. Most kit cables are slim enough to pass under a door seal without preventing it from closing properly.
A purpose-made flat cable designed specifically for this purpose is worth using if yours is not already suitable. These cables are typically 3 to 5mm thick and designed to pass under a door or window frame without damaging the seal or creating a draught gap. They cost around £10 to £20 and make the installation significantly neater.
Do not force a thicker cable under a door frame and rely on the door compressing it. Over time this damages both the cable insulation and the door seal, and a pinched cable is a potential fire risk.
Garden installation: through an exterior wall
For a garden or ground-mounted panel, the cable typically needs to pass through or under an exterior wall to reach an indoor socket. The cleanest route is through an existing cable entry point if one exists — a hole from a previous satellite dish or aerial installation, for example.
If you need to create a new entry point, this is a job for a registered electrician, who will fit a proper cable gland and ensure the penetration is weatherproofed. Do not drill through walls yourself for electrical cable entry without relevant competence and appropriate sealant.
An outdoor socket in the garden eliminates the need for a long cable run entirely. Many households have outdoor sockets already. If yours does not, having one installed by an electrician at the same time as the solar connection is often the tidiest solution.
Shed or outbuilding installation
If your panels are on a shed roof or outbuilding, the cable run to the house can be longer. Cables run outside over any distance should be rated for outdoor and UV exposure. Standard indoor cable will deteriorate over months of UK weather. Use cable rated for outdoor use and protect long runs in conduit where possible, particularly if the cable crosses a path or lawn.
Cable length and extension leads
Avoid using indoor extension leads to extend the cable run from your microinverter. Standard extension leads are not rated for outdoor use and are not designed to carry the sustained low-level current from a solar microinverter for hours at a time. If your cable is not long enough to reach an appropriate socket, the right solution is either an outdoor-rated extension specifically designed for solar use, or repositioning the system closer to an accessible socket.
Tidying up the cable
Cable clips rated for outdoor use are cheap and make a real difference to how the installation looks and how safe it stays long term. Clip the cable at regular intervals along any wall or railing run to prevent it flapping in wind. Where the cable changes direction, a clip either side of the bend prevents repeated stress on the cable at that point.
Taking an extra hour on the cable run when you first install the system is much easier than dealing with a tangled, damaged or weathered cable six months later. For more on setting up your system from scratch, the Getting Started guide covers the full process.