Solar Panel Wiring Nepal: Inverter Install Guide

Solar panel wiring in Nepal: what the job actually involves

Solar panel wiring Nepal homeowners trust is not just a pair of cables from the roof to a box on the wall. A safe home solar system has a DC side on the roof, an AC side after the inverter, protective isolators on both, a proper earth electrode, and a changeover arrangement that works cleanly with your Nepal Electricity Authority (NEA) supply. Get any one of those wrong and you risk fire, shocked users, or an inverter that keeps faulting in the monsoon.

SDR Smart Design and Repair handles the electrical half of home solar across Kathmandu, Lalitpur and Bhaktapur: array string wiring, DC and AC isolators, earthing pits, hybrid inverter installation Kathmandu projects, load-side connections and changeover switching. We work alongside your solar company or take the full electrical scope when they only supply panels. Call or WhatsApp 9801508528 to talk through your layout before anything is fixed to the roof.

• DC string wiring from panels to isolator to inverter
• AC output wiring from inverter to changeover and DB
• Lightning and equipment earthing with a tested electrode
• NEA-compatible changeover and meter-side coordination
• Cable sizing, glanding, labeling and as-built circuit schedule

The DC side: panels, string voltage and isolators

Everything from the panel terminals up to the inverter DC input is the DC side, and it behaves differently from house wiring. Open-circuit voltage on a string of panels can climb well above 400–600 V DC depending on how many modules are in series, so cable selection, connector quality and isolation points matter more than most people expect.

String design starts with voltage, not wattage. Panels in series add their voltages; panels in parallel add their currents. Your inverter has a maximum input voltage — exceed it on a cold clear morning and the unit can fail permanently. That is why we calculate the worst-case Voc with temperature correction before cutting any cable. Home solar electrical work Nepal typically uses 6 mm² or 10 mm² solar cable (UV-rated, double insulated) for DC runs, with MC4-compatible locking connectors crimped with the correct tool, not pliers.

A DC isolator is non-negotiable. It goes between the array and the inverter (and often a second one at the array side) so the roof can be de-energised for maintenance without walking to the garage. We mount isolators in shaded, reachable locations — not sealed under a hot tin roof where the plastic bakes and cracks within two seasons. Bus bars and terminal torques inside combiner boxes are checked and recorded, because loose DC terminals are a leading cause of rooftop hot spots.

• Series string stays inside inverter max input voltage at coldest expected temperature
• UV-rated solar cable for all outdoor DC runs, clipped away from sharp edges
• Locking MC4-style connectors crimped with a dedicated tool
• DC isolator within sight of the inverter, plus array-side isolation where required
• No joint buried in the roof space — every connection accessible and labeled

The AC side and hybrid inverter wiring Nepal homes need

After the inverter converts DC to 230 V / 50 Hz, the AC side enters your distribution world: changeover switch, main DB, meter, NEA line. Hybrid inverter wiring Nepal projects add a battery bank on a third circuit, with its own DC breaker or fuse, isolator and carefully sized interconnect cable — see our companion guide at /blog/inverter-battery-wiring-nepal for the battery-room details.

AC cable sizing follows load, not panel capacity. A 5 kVA hybrid inverter at full output draws roughly 22 A, which sits on a 4 mm² copper conductor protected by a suitable 32 A device in typical ambient conditions; longer runs need a size up for voltage drop. The inverter output must never back-feed an open NEA neutral unless the unit is certified for anti-islanding and the changeover logic is correct. We land the inverter on a dedicated way in the DB with its own MCB or RCBO, clearly labeled, so a fault isolates one circuit instead of darkening the house.

Earthing ties both sides together safely. The inverter chassis, the array frame, the mounting rails and a lightning protection down-conductor (where fitted) all bond to the same earth electrode system. Bonding only to a plastic water pipe or a random rebar stub is not earthing — we install or upgrade a proper pit, measure resistance and hand you the reading. Kathmandu soil varies widely; 10 ohms or lower is a common target for equipment earth, and better for lightning-prone rooftops.

• Dedicated AC breaker sized to inverter output and cable run length
• Anti-islanding changeover that separates you from the NEA grid safely
• Common earth electrode for array frame, inverter chassis and house DB
• Resistance test recorded after installation
• Labeled AC and DC ways in the distribution board

Changeover with NEA: grid-tie, hybrid and manual options

Nepal runs on the NEA grid, and most homes want solar to supplement it rather than replace it. The changeover arrangement decides what happens when the grid drops, when the battery is full, and when you need to bypass a faulty inverter entirely.

Three approaches cover almost every Kathmandu installation. First, a pure grid-tie system with no battery: when NEA power fails, the inverter shuts down by regulation and the house goes dark unless you have a separate backup path. Second, a hybrid inverter with built-in transfer: it can island your essential loads on battery within milliseconds and reconnect when NEA returns — the most common upgrade we wire today. Third, a manual or motorised changeover switch that lets you flip the house between solar/inverter output and direct NEA supply for servicing. We recommend the third option even on hybrid installs, because one switch position of pure grid bypass means an inverter fault never leaves you waiting on parts.

Meter-side work is NEA territory. We do not touch the service conductor or meter seals; instead we coordinate the load-side connection so inspectors see a clean, compliant install. If your existing service is undersized for a new AC output plus the original load, that is a panel upgrade conversation — start at /services/panel-upgrades.

• Grid-tie only: no backup when NEA supply drops
• Hybrid with battery: essential loads ride through outages
• Manual bypass changeover: always keep a grid-only position
• NEA meter and service work stays with the authority, not your installer

When you need an electrician versus a solar company

A solar company designs the array, supplies panels and usually commissions the inverter. An electrician owns everything hard-wired into your building: cable routes, breakers, earthing, changeover, load calculations and the final connection to your DB. In practice the cleanest projects split the scope that way — and the messiest ones try to skip the electrical half.

Call the solar company first for panel choice, mounting rail layout, string design and inverter warranty registration. Call SDR when you need conduit routes from roof to DB, an earth pit, DB ways added or replaced, a changeover switch, three-phase balancing, or a repair because someone used house cable on the DC side. If your board is already full or running hot, our team at /services/panel-upgrades handles the upgrade before the inverter lands. New builds and full renovations should book electrical installations early so solar conduits are chased into the walls instead of surface-mounted later — details at /services/electrical-installations.

Red flags worth pausing on: aluminium DC cable, isolators taped into the roof space, no earth electrode at all, a changeover wired so NEA and the inverter can fight each other, or an inverter bolted above a water tank. Any of those deserves a professional inspection before first power-on.

• Solar company: panels, rails, string design, inverter commissioning
• Electrician: DB work, isolators, earthing, changeover, load side
• Both: roof survey, cable routes, coordinated commissioning
• SDR covers the electrical scope in Kathmandu Valley — 9801508528

Cost cues and booking your solar electrical work

Electrical-only solar work in Kathmandu typically lands between NPR 15,000 and NPR 45,000 for a single-phase home depending on cable runs, whether an earth pit is needed, and if the distribution board must be upgraded. Three-phase homes, multi-string commercial roofs and new changeover panels sit higher. Panel and inverter hardware is quoted separately by your solar supplier — we give an itemised electrical price so nothing is buried.

SDR Smart Design and Repair works in Kathmandu, Lalitpur and Bhaktapur six days a week, with emergency call-outs when a commissioning fault cannot wait. Every job includes labeled circuits, torque checks and a walk-through so you know how to isolate the system yourself. Ready to plan the wiring properly? Book a visit through /#booking or send photos of your roof and DB on WhatsApp to 9801508528 for a quick feasibility check.

• Single-phase electrical scope: from about NPR 15,000
• Typical full electrical package: NPR 15,000–45,000
• Earth pit, DB upgrade or three-phase work quoted on inspection
• Book at /#booking or WhatsApp 9801508528