The 10 Fatal Mistakes in Photovoltaic Installation (+ Solutions)

4. Underestimating the Importance of Wiring and Electrical ProtectionsSafety and Performance: Proper Wiring Is MandatoryWiring represents 8 to 12% of the total cost but determines 100% of the safety. Wiring errors are the cause of 65% of electrical incidents on PV installations.Common mistakes:Insufficient cable cross-section: overheating, line losses (up to 5% of production)Non-compliant cables: use of standard domestic cables instead of UV-resistant PV cablesNo DC protections: no disconnect switch, fuses, or surge protector on the DC sidePoor tightening of MC4 connectors: contact resistance, risk of electric arcAccurately Calculate the Required Cable Cross-SectionCable sizing is not improvised: a cross-section that is too small generates continuous financial losses for 25 years, while an oversized cross-section represents an unnecessary extra cost. Voltage drop must never exceed 3% between the panels and the inverter.🔌 FREE PROFESSIONAL TOOLCalculate the optimal cable cross-section for your installation in 2 minutes⚡ VOLTAGE DROP CALCULATOROur free calculator takes into account all the essential parameters:Exact distance between panels and inverterOperating voltage of your installation (12V, 24V, 48V, high voltage)Maximum current and transmitted powerType of current (DC for panels-inverter, AC for inverter-grid)Ambient temperature and correction factorInverter-panel distanceRecommended minimum cross-sectionLine losses0-10m4 mm²< 1%10-20m6 mm²< 2%20-30m10 mm²< 3%> 30mSpecific studyHigh risk“Professional wiring with suitable cross-sections and compliant protections guarantees safety for 25 years. It's a €200-300 investment that protects a €10,000 system. Use our free calculator to avoid any sizing errors.” — Wattuneed Design OfficePhotovoltaic Cables: Mandatory SpecificationsWarning: Domestic cables H07V-K or U-1000 R2V are NOT suitable for a photovoltaic installation. You must imperatively use specific PV cables (EN 50618 standard or equivalent) featuring:UV and weather resistance (outdoor lifespan 25+ years)Operating temperature -40°C to +90°C (up to +120°C peak)Double reinforced insulationResistance to ozone and chemicalsLow smoke emission in case of fireEssential Electrical ProtectionsEvery installation must include:DC side (direct current): disconnect switch, overcurrent protection, Type II surge protectorAC side (alternating current): 30mA Type A residual current circuit breaker, decoupling protectionGrounding: < 30 Ω required, equipotential bondingRefer to the detailed Wattuneed wiring diagrams for an installation compliant with NF C 15-100 and IEC 62548 standards.⚠️ Concrete Example of a Costly Mistake:5 kWp installation 25m from the inverter with 4mm² cable: 4.5% loss, i.e. €225/year. Over 25 years = €5,625 lost. A 10mm² cable would have cost €180 more at installation. Calculate your case →