10kW Solar System Cable Size — DC, AC and Earth (Pakistan)

Three runs, and the one that depends on your supply

A 10 kW array has the same three electrical jobs as a small one: single-core DC outdoors from the panels to the inverter, multi-core AC from the inverter into the house, and an earth for the frames. What is different at 10 kW is that the AC side is no longer a foregone conclusion. Plenty of 10 kW homes in Pakistan run a single-phase 220 V connection; plenty run 400 V three-phase. The inverter follows the connection, and the cable follows the inverter.

A 10 kW rooftop array in Pakistan needs 6 mm² single-core DC per string, stepping to 10 mm² where two strings are combined into a home run longer than 43 m; 4 mm² four-core copper on a 20 A MCB where the inverter is three-phase, or 16 mm² on a 63 A MCB where it is single-phase; and 10 mm² for the array frame bonding and the inverter earth. Those sizes hold for two strings of ten panels at 17.5 A of design current each, routes of 86 m or less on the DC side, and cable clipped direct at 30°C ambient.

The runs in a 10 kW rooftop array, two strings of ten panels. Current capacity per BS 7671, installation reference method C (clipped direct), 30°C ambient; conductor data per IEC 60228. DC and single-phase AC figures are for two loaded conductors, three-phase for three. Derate for conduit, bunching and roof heat. Verify sizing with a licensed electrician or your solar installer.
Run	Current	Cable	Capacity	Protection
Each panel string, DC	17.5 A design	6 mm² single core	46 A	DC isolator
Both strings combined, DC	35 A design	6 mm² to 43 m route, else 10 mm²	46 A / 63 A	DC isolator, string fuses
Inverter to AC board, 3-phase 400 V	14.4 A/phase	4 mm² 4 core	32 A	20 A MCB
Inverter to AC board, 1-phase 220 V	45.5 A	16 mm², 2 core plus a separate earth core	85 A	63 A MCB
Array frames and inverter earth	—	10 mm²	—	—

Working the DC size out, step by step

Two numbers off the back of your own panels drive this: the short-circuit current, Isc, and the voltage at maximum power, Vmp. The worked example below uses a plate reading Isc 14 A and Vmp 37 V, twenty panels split into two series strings of ten, and a 30 m route from the roof edge down to the inverter.

String current. Panels in series all pass the same current, so each string of ten carries one panel's Isc: 14 A. Adding panels to a string does not add current.
Design current. Size on 1.25 × Isc, because panels beat their plate figure on a bright, cold morning and hold it: 14 × 1.25 = 17.5 A per string.
String voltage. Ten panels in series: 10 × 37 = 370 V at maximum power.
Voltage budget. 3% of 370 V is 11.1 V — double the budget a 5 kW system gets, from the same cable.
The drop on 6 mm². 7.3 × 17.5 × 30 ÷ 1000 = 3.83 V over the 30 m route, which is 1.0% of 370 V. A third of the budget spent.
Heat check. 6 mm² is rated 46 A clipped direct at 30°C against 17.5 A design current, so heat is not the constraint on a string. Combine two strings and capacity starts to bite — 2.5 mm² drops out at 35 A — but 6 mm² still has 11 A in hand.

This is the counter-intuitive part of a big array: 4 mm² also passes at 30 m, because the 370 V string can afford 11.1 V of drop. We still put 6 mm² on a 10 kW roof, and the reason is in the paralleled column of the next table — combine two strings and 6 mm² still works where 4 mm² does not. The millivolt figure covers the trip out and the trip back, so the 30 m in that sum is the route, one way, and the cable you buy is twice it per pair.

How long a run each size covers

The 370 V string is what buys the distance here. Compare these numbers with a 5 kW array on 185 V strings and every figure doubles — the bigger system is easier on cable, not harder.

Longest one-way route at 3% voltage drop on a 370 V string (10 × 37 V), at 17.5 A for one string and 35 A with two strings combined. Buy twice these lengths per pair — the positive and the negative both travel the route. Voltage drop and current capacity per BS 7671, method C, 30°C, PVC; conductor data per IEC 60228. Recalculate for your own string current and voltage. Verify with a licensed electrician.
Size	Capacity	Voltage drop	Route, one string (17.5 A)	Route, two combined (35 A)
2.5 mm²	27 A	18 mV/A/m	35 m	not enough capacity
4 mm²	36 A	11 mV/A/m	57 m	28 m
6 mm²	46 A	7.3 mV/A/m	86 m	43 m
10 mm²	63 A	4.4 mV/A/m	144 m	72 m
16 mm²	85 A	2.8 mV/A/m	226 m	113 m

2.5 mm² is struck out of the combined column on capacity, not on distance: 27 A of rating against 35 A of design current fails before voltage drop is even considered. Full spec and today's rate sit on the 6mm solar cable and 10mm DC cable pages.

The AC side: three-phase and single-phase

Three-phase, 400 V. The inverter splits its output across three phases: 10000 ÷ (1.732 × 400) = 14.4 A per phase. With the 1.25 continuous-duty margin that is 18 A, so a 20 A MCB. 4 mm² four-core copper carries 32 A with three loaded conductors, 12 A clear of the breaker. Over a 15 m route at 14.4 A the drop works out at 11 × 14.4 × 15 ÷ 1000 = 2.38 V, about 0.6% of 400 V. The tabulated millivolt figures are the two-conductor values, and a three-phase run drops about 13% less than that (√3 ÷ 2 = 0.87), so using them here is the conservative way round.

Single-phase, 220 V. The whole output goes down two conductors: 10000 ÷ 220 = 45.5 A, times 1.25 is 56.9 A, so a 63 A MCB. Here is where quotes go wrong. 10 mm² carries exactly 63 A on two loaded conductors — the same number as the breaker, with nothing left after the cable enters conduit or the ambient passes 30°C. 16 mm² at 85 A is the size to run, and its drop over 15 m is 2.8 × 45.5 × 15 ÷ 1000 = 1.91 V, under 1%. Voltage drop was never the problem on that run; breaker margin was.

Bond the array frames and the inverter body back to the house earth electrode with 10 mm² — every frame, not just the first, because a clamp on anodised aluminium is not a reliable electrical joint. The solar earthing cable guide covers the terminations. If the system is going on net metering, the run from the AC board on to the utility meter is sized separately: see the net metering cable size guide.

A 370 V string is live in daylight whether the inverter is switched on or off, and a DC arc at that voltage does not self-extinguish the way an AC one does. Size the cable, the DC isolator and the string fusing together as one design, and have a licensed electrician or your solar installer confirm it before anything is energised.

How many metres of cable a 10kW roof takes

At 10 kW the quantity matters more than the size. Two strings send two pairs of conductors down the same long route, and the earth bonding alone crosses the whole array. Here is the count for one stated layout, to adjust against your own roof.

Cable count for one stated layout: twenty panels in four rows of five on the roof slab, wired as two series strings of ten, both brought to the roof edge and run down to a three-phase inverter at ground level with the AC board beside it. DC rows need twice the route length per pair. Cable figures are the bare doubled route — add about 15% on top for slack, bends and re-terminations. Measure your own routes before ordering.
Run	Route	Cable to buy	Size
String 1 to roof edge, DC	8 m	16 m (8 red, 8 black)	6 mm²
String 2 to roof edge, DC	6 m	12 m (6 red, 6 black)	6 mm²
Roof edge to inverter, DC, both strings	30 m	120 m (2 pairs)	6 mm²
Inverter to AC board, three-phase	12 m	12 m of 4 core	4 mm²
Frames, inverter, earth pit	38 m	38 m single core	10 mm²

Totals for that layout: 148 m of 6 mm² DC split evenly red and black, 12 m of 4 mm² four-core, and 38 m of 10 mm² earth. With 15% for slack, order 85 m of each DC colour. Two things to check before comparing quotes: coil lengths in this market are not standard, and price lists routinely print a coil price where a per-metre price belongs. Ask for the metres and ask which unit the number is in. Send us the route lengths on WhatsApp and we will quote the metres.

The cable for this job

Coiled black and red single-core solar DC cable, with an inset showing the stranded copper conductor cut back from the insulation

10MM² · 1 CORE · DC SOLAR · 80/0.40 CLASS 5

10mm DC Solar Cable

The size for a combined home run at 35 A and for the array earth on a system this big. Single-core stranded copper, plain annealed class 5, 80 strands of 0.40 mm — not tinned. A 100 m length holds about 8.89 kg of conductor at 88.9 kg/km, which is the fastest check on whether you were sold full copper: put the coil on a scale.

Factory-direct price

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Prices track the daily copper rate. Send the metres and your city on WhatsApp for the exact figure.

The strings themselves take 6mm solar cable; a three-phase AC run takes 4mm 4 core and a single-phase one takes 16mm, 2 core plus a separate earth core, both off the standard cable range; and the earth takes 10mm earth cable. All DC and solar cable sizes.

Current capacities on this page assume the cable is clipped direct in open air at 30°C. A run pulled through conduit, bunched with other circuits, on a roof slab in June carries less than the table says. Have a licensed electrician or your solar installer confirm the size for your layout — or start with the cable size calculator.

Frequently asked

10kW solar system ke liye kitna cable chahiye?

For the layout on this page it comes to 148 m of DC cable, 12 m of four-core AC and 38 m of earth. The 30 m route from the roof edge down to the inverter alone accounts for 120 m of it, because two strings send two pairs of conductors down the same path. Measure your routes, double them per pair, then add about 15%.

Is a 10kW inverter single-phase or three-phase, and does the cable change?

Both are sold in Pakistan, and the AC cable changes a great deal. On a 400 V three-phase supply the inverter puts out 14.4 A per phase, which is a 20 A MCB and 4 mm² four-core. On 220 V single-phase it puts out 45.5 A, which is a 63 A MCB and 16 mm². Check the inverter's nameplate before ordering AC cable.

Why does a 10kW array use the same DC cable as a 5kW?

Because you double the panels in series, not in parallel. Ten panels in a string carry the same 14 A as five panels in a string; what doubles is the voltage, from 185 V to 370 V. Voltage drop is judged as a percentage of that voltage, so the bigger system is actually easier on cable, not harder.

What MCB size for a 10kW inverter?

20 A per phase on three-phase supply: 10000 ÷ (1.732 × 400) = 14.4 A, times the 1.25 continuous-duty margin is 18 A. On single-phase it is 63 A: 10000 ÷ 220 = 45.5 A, times 1.25 is 56.9 A. That single-phase case is the one to watch, because 10 mm² carries exactly 63 A and leaves nothing in hand.

Can I combine the two strings into one home run?

Yes, through a combiner box with fusing, and it saves you a pair of conductors down the long route. The cost is current: the home run then carries 35 A instead of 17.5 A, so 6 mm² drops from 86 m of allowable route to 43 m, and past that the home run wants 10 mm². Work out which is cheaper for your route.

What size earth wire for a 10kW solar array?

10 mm² for the array frame bonding and the inverter body on a system this size, run back to the house earth electrode. Every frame in the array gets bonded, not just the first one — the panels are clamped to anodised aluminium and the clamp is not a reliable electrical joint. The solar earthing cable guide covers the terminations.

Cable for the 10kW array, at the factory rate

We draw the copper in Lahore and sell it at the day's rate — no dealer margin. Send the route lengths and whether the inverter is single or three-phase: Punjab in 1–2 days, rest of Pakistan in 2–4.

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