Solar cable and wire sizing for Pakistan

The cheapest way to ruin a good system

Panels have a brand on them. Inverters have an app. Cable is invisible, buried in a conduit, and no visitor ever asks about it. That is precisely why it is the first thing shaved when a quote needs to come down by PKR 40,000, and it is the single worst place to save money in a rooftop solar build.

Wiring for a normal Lahore home comes to roughly PKR 25,000 for around 90 metres of DC cable and 20 metres of AC cable, plus about PKR 35,000 for the electrical items kit of breakers, fuses, isolators, glands, MC4 connectors and conduit. On a 5kW system installed at PKR 700,000 to PKR 900,000, that is under 8 percent of the job. Cutting it in half saves PKR 30,000 and puts the other PKR 800,000 at risk.

Solar DC cable is a specific product, not just thick wire

What gets sold in Pakistan as solar cable, when it is genuine, is a cross linked polyolefin insulated single core cable rated 1000V or 1500V DC. Four properties separate it from the PVC house wire sitting next to it on the shop shelf.

• Voltage rating. A string of 14 panels in series sits around 500 to 570 volts DC on a cold morning. House wire is rated 450 or 750 volts AC and is not qualified for that at all.
• UV and ozone resistance. Panel tails and interconnects live in direct Lahore sun for twenty five years. PVC insulation goes chalky, cracks, and starts flaking off within two summers on an exposed roof.
• Temperature rating. A black cable clipped to a hot steel rail under a panel in June reaches 70 to 80 degrees ambient. Solar cable is rated 90 degrees continuous, 120 degrees short term. PVC is rated 70 degrees, so it is already past its limit before any current flows.
• Tinned copper strands. The tin coating resists the oxidation and sulphidation that Lahore's air, particularly through the smog season from November to January, does to bare copper. Bare copper strands turn black and green at crimp points and the joint resistance climbs.

Price wise, genuine 4sqmm tinned copper solar DC cable in Lahore runs about PKR 220 to PKR 320 per metre in 2026 depending on brand, and 6sqmm sits around PKR 320 to PKR 460. Counterfeit product is widespread. The usual tell is weight, because a coil of real tinned copper is noticeably heavier than a coil of copper clad aluminium sold at the same nominal size, and a cut end shows silver strands throughout rather than a copper coloured core under a thin plating.

4sqmm or 6sqmm: how to actually decide

Two things drive the choice. Current carrying capacity, which is about not overheating, and voltage drop, which is about not wasting energy over distance. Ampacity is rarely the binding constraint on a domestic string. Voltage drop usually is.

The rule most Pakistani installers work to is keeping DC side voltage drop under 2 percent, and AC side drop under 2 percent as well, so the whole path loses no more than about 4 percent. Here is what that means for real runs.

String current	One way run	4sqmm drop	6sqmm drop	Choice
13 A at 500 V	15 m	0.28 percent	0.18 percent	4sqmm is fine
13 A at 500 V	30 m	0.55 percent	0.37 percent	4sqmm is fine
13 A at 500 V	60 m	1.11 percent	0.74 percent	4sqmm acceptable, 6sqmm better
26 A at 500 V, two strings paralleled	40 m	1.48 percent	0.99 percent	6sqmm
13 A at 120 V, short low voltage string	25 m	3.9 percent	2.6 percent	6sqmm, or restring higher
110 A at 48 V, battery cable	2 m	Not suitable	Not suitable	25sqmm to 35sqmm

Two things jump out of that table. First, high voltage strings are forgiving. Because a modern string runs at 400 to 570 volts, the current is low and the percentage drop is tiny even over long roof runs. Second, low voltage circuits are brutal. Battery cabling at 48 volts carries eight to ten times the current of a string at the same power, which is why battery leads are the fattest cables in the house.

Where long runs actually happen in Lahore

Most homes need 25 to 40 metres of DC cable per string, and it is never the straight line distance. The cable goes from the array across the roof, around the water tank plinth, down the stair block wall, along a corridor, and into the inverter. On 1 kanal houses in DHA and Bahria Town, where the array sits on the back block and the inverter is in the front store room, 60 metre runs are routine. That is when 6sqmm earns its price.

The opposite case turns up in older parts of the city. Narrow houses in Gulberg back streets and around Mughalpura often have the inverter mounted on the stair landing directly below the array, so the run is 12 metres and 4sqmm is more than enough.

The AC side is where the sizing gets missed

Attention goes to the fancy DC cable and the AC side gets whatever cable was left over from the house wiring. This is backwards. A 5kW inverter at 230 volts delivers about 22 amps continuously, which is a serious current for a domestic circuit and it flows for six to eight hours a day, every day, for decades.

Reasonable practice for AC output cable in Lahore:

1. 3kW single phase inverter, up to 15 metres: 4sqmm three core copper.
2. 5kW single phase inverter, up to 15 metres: 6sqmm three core copper.
3. 5kW single phase inverter, 15 to 30 metres: 10sqmm three core copper.
4. 10kW three phase inverter, up to 20 metres: 10sqmm four core copper minimum.

The other AC side detail that gets skipped is the breaker. An inverter output needs its own dedicated MCB sized above the continuous current but below the cable rating, plus a lockable isolator so the LESCO inspector and any future electrician can safely disconnect the system. Applications for net metering get delayed over a missing isolator more often than anything else.

DC arcs are the reason this matters more than it looks

An AC circuit crosses zero volts a hundred times a second, and an arc drawn in an AC circuit tends to extinguish itself at those crossings. DC never crosses zero. A DC arc, once struck, keeps burning as long as the source can feed it, and a solar array in full sun is an excellent source. The arc temperature is high enough to melt copper and set fire to anything nearby.

What actually causes those arcs on Lahore rooftops, in order of how often it turns up on service calls:

• Badly crimped MC4 connectors. Crimped with pliers instead of the proper tool, so the joint has resistance, so it heats, so it oxidises, so the resistance rises further. Mixed brand MC4 pairs are almost as bad, because the pin diameters differ by fractions of a millimetre and the contact is poor.
• Ordinary house wire used on the DC side. Insulation cracks under UV, two conductors touch across a wet roof after monsoon rain, and there is nothing to interrupt the fault.
• Undersized cable on a paralleled string that runs warm all summer, ages the insulation faster, and eventually fails at a bend or a clip point.
• Unprotected cable dragged across a parapet edge without conduit, chafing a little further every time the wind moves it.

None of these are exotic failures. Every one of them is on a roof somewhere in this city right now. The fix is routine: proper cable, a proper crimp tool, matched connectors, UV rated conduit or cable tray on every exposed run, and DC fuses on parallel strings.

The honest caveat

Oversizing cable is not free and there is a limit to how useful it is. Going from 4sqmm to 6sqmm on a 25 metre run gains around 0.2 percent of annual energy, which on a 5kW system is roughly 15 units a year, worth about PKR 900. The cable upgrade itself costs PKR 5,000 or more. On that basis the upgrade never pays back on energy alone. It pays back on thermal margin, on insulation life, and on having headroom if the array is expanded later, which in Lahore it very often is. Buy one size up for future proofing, not for the voltage drop arithmetic.

Conduit, routing and the monsoon

Cable protection matters as much as cable size in this climate. Exposed DC cable should run in UV stabilised conduit or a covered tray, not in the flexible grey PVC pipe that turns brittle after eighteen months of Lahore sun. Conduit runs need a drain point at the low end, because rainwater always finds its way in and standing water inside a conduit will sit against the insulation for months.

Cable ties are another quiet failure. Ordinary white nylon ties fail in about two years on a Lahore roof, and then the cable sags into a puddle or onto a sharp edge. Black UV stabilised ties, or better still stainless clips on the structure, are worth the small extra cost. Positive and negative should run bundled together along the same path, which also cuts induced surge pickup as described in the earthing and lightning protection article.

What to check on a quote

A quote that says wiring, lump sum, PKR 15,000 is not telling anyone anything. A proper bill of quantity names the cable size, the length, whether it is tinned copper, the voltage rating, the connector brand, the conduit type, and the breaker and fuse ratings. If that detail is absent, ask for it in writing before signing.

Anyone comparing quotes should also read the 2026 installation cost breakdown and the Lahore companies comparison. For system level pricing see the 5kW article or the 8kW article. Battery cable specifics are covered in the bank sizing guide, and our installation service and repair service pages explain what is included as standard. Size a system first on the calculator, then get in touch.