When comparing two solar quotes, the cheaper one is often cheaper because of what you can’t see in the photos: thin cables, missing breakers, no surge protection. These parts cost little, but they protect a system worth lakhs.
- Proper solar DC cable (UV-resistant, tinned copper), correctly sized.
- DC breaker or isolator between panels and inverter.
- DC and AC surge protection devices.
- Genuine MC4 connectors, properly crimped.
Solar DC cable
The cable from panels to inverter carries DC at high voltage, sits in the sun for decades and faces heat, rain and UV. Normal house wire isn’t made for that.
- Use proper PV cable, typically tinned copper with UV-resistant double insulation.
- Common home sizes are 4mm² or 6mm², depending on current and distance.
- Long cable runs need thicker cable to limit voltage drop.
- Run cables in conduit or trunking, not loose on the roof.
DC breaker or isolator
You need a way to cut panel power to the inverter for service or emergencies. A DC-rated breaker or isolator, rated for your string voltage, does that. AC breakers are not a safe substitute, DC arcs behave differently.
Fuses for multiple strings
If you have several strings in parallel, fuses protect each string from current flowing back into it from the others during a fault.
Surge protection devices (SPDs)
SPDs divert lightning-induced and grid surges to earth. You want one on the DC side and one on the AC side. They only work if the system is properly earthed, see our earthing guide.
Battery cables and fuse
Battery cables carry very high current at low voltage. They must be thick, short and fused near the battery. Undersized battery cables heat up, waste energy and can be a fire risk.
MC4 connectors
These clip panel cables together. Cheap copies or bad crimping cause hot spots and melted plugs, often found years later. Use matching genuine connectors and a proper crimping tool.
A tidy DC box tells you a lot
Open the DC distribution box. Labelled breakers, an SPD, neat cable glands and an earth connection mean the installer cared. A tangle of wires with tape means you should ask questions. Our guide to spotting fakes covers more warning signs.
Want a second opinion on a quote?
Send the itemised quote. We’ll tell you if the protection parts are there.