Solar Panel Wiring: How Panels Connect to Your Home

From roof to appliance, the electricity flows through:

1. Solar panels — generate DC electricity from sunlight 2. MC4 connectors — weatherproof connectors linking panel to panel 3. DC cable — carries DC electricity from panels down to the inverter 4. DC isolator switch — safety disconnect between panels and inverter (accessible from ground level) 5. Inverter — converts DC to AC and manages the system 6. AC isolator switch — safety disconnect between inverter and consumer unit 7. Consumer unit (fuse box) — distributes electricity to your home's circuits 8. Generation meter (if required) — records total electricity generated 9. Smart meter — records import from and export to the grid

If you have a battery: The battery connects to the inverter (or has its own dedicated inverter). The inverter manages charging and discharging automatically.

If you have an EV charger: The charger connects to a dedicated circuit in the consumer unit — it draws from whatever source is available (solar, battery, or grid).

Source: IET Wiring Regulations BS 7671; MCS installation standards.

Series wiring (most common for string inverters): - Panels connect positive-to-negative in a chain (like batteries in a torch) - Voltage ADDS up: 10 panels at 40V each = 400V DC total - Current stays the same: ~10A - Used with: string inverters, SolarEdge optimisers - Advantage: thinner cables (lower current = less copper needed) - Disadvantage: one underperforming panel affects the entire string

Parallel wiring (less common for residential): - Panels connect positive-to-positive, negative-to-negative - Voltage stays the same: 40V - Current ADDS up: 10 panels at 10A = 100A - Used with: some off-grid systems, charge controllers - Advantage: each panel independent (shading does not affect others) - Disadvantage: requires thicker cables (higher current)

Micro-inverter wiring: - Each panel has its own micro-inverter on the back - DC conversion happens at the panel — only AC flows to the house - Panels connect in parallel on the AC side - Each panel is fully independent - Advantage: best performance in shading, simplest panel expansion - Disadvantage: more components on the roof

For most UK residential installations: Series wiring with a string inverter is standard. Optimisers or micro-inverters are added for partially shaded or multi-orientation roofs.

Source: Electrical engineering fundamentals; MCS wiring standards.

Solar panel DC circuits carry HIGH VOLTAGE (300–600V DC on a typical 10-panel string) whenever the panels are illuminated. This presents serious risks:

DC is more dangerous than AC at the same voltage: - DC arcs do not self-extinguish (AC arcs extinguish 100 times per second) - DC shocks are harder to let go of (muscle contraction is continuous) - DC arc faults are a fire risk if connectors are improperly crimped

Panels cannot be 'switched off' at the panel level: - Even with all isolators switched off, the cables between panels and the DC isolator are LIVE during daylight - Covering panels with a blanket reduces but does not eliminate voltage - Only qualified electricians should work on DC solar circuits

AC side risks: - The inverter connection to the consumer unit involves 230V AC - This is the same voltage as mains electricity — lethal if contacted - Part P Building Regulations require qualified electricians for this work

The message: Solar wiring is not a DIY job. The DC side is dangerous and the AC side is legally restricted. Use an MCS-certified installer.

Source: HSE electrical safety guidance; IET Wiring Regulations.