· 4 min read
Solar panels are sold with 25-year warranties. The cable between them sits in the same sun, rain and heat for just as long, and it carries direct current, which does not pass through zero the way mains current does. House wire is not designed for either of those things.
What goes wrong with PVC wire outdoors
- UV light breaks down ordinary PVC. Within a few summers the insulation turns brittle and cracks, exposing the conductor.
- Heat on a roof can push cable temperatures well above what PVC is rated for, especially in Indian summers.
- DC faults are harder to extinguish than AC faults. Damaged insulation on a DC string can sustain an arc, which is a serious fire risk.
What solar cable does differently
| Part | Solar DC cable | Why |
|---|---|---|
| Conductor | Tinned copper | Resists corrosion at crimped connectors |
| Insulation and sheath | Cross-linked polyolefin (XLPO) | Stays flexible in heat and cold, does not melt |
| Weathering | UV and ozone resistant | Built for decades in direct sun |
| Fire behaviour | Zero halogen | No corrosive gas if it burns |
EN 50618 is the European standard written specifically for photovoltaic cables, and it covers all of these properties. Newtek solar cable conforms to EN 50618 and is TÜV certified.
Choosing a size
Most residential strings use 4 sq mm. Long runs, or runs carrying combined strings to the inverter, may need 6 or 10 sq mm to keep voltage drop low. Because DC string voltages are high and currents modest, every volt lost in the cable is energy you paid for and never use. Try our voltage drop calculator as a first check, then confirm with your installer.
Installing it well
- Keep positive and negative runs close together to reduce induced voltages from lightning.
- Support cables so they do not rub on sharp panel frames or lie in standing water.
- Use connectors rated for the cable size and crimp them with the correct tool.
- Do not mix solar cable and house wire on the same DC run.
See sizes and construction on the solar DC cable page.