What size cable for a UPS or inverter — the AC side, the DC side, and the changeover

PILONE CABLES TECHNICAL TEAM

Size the AC cable on the VA rating: 2.5 mm² up to 2000 VA, 4 mm² at 3000 VA, 6 mm² at 5000 VA.

The AC current is the rating divided by 220 V, so a 1000 VA unit is 4.5 A and a 5000 VA unit is 22.7 A, and the same size serves both AC runs — mains into the inverter, and inverter out to the backup board. The thick short cable between the inverter and the battery bank is a different job on a different voltage, and it is sized in the inverter battery cable guide.

Three runs, and only two of them are on this page

Most of the confusion about inverter cable is that one install has three separate runs and people quote one size for all of them. They carry different currents at different voltages.

The three cable runs on a single-phase home UPS or inverter install. AC currents are the unit's VA rating ÷ 220 V; the DC figure is the same VA ÷ the nominal battery voltage, before losses. Verify sizing with a licensed electrician for your installation.
Run	What it carries	Voltage	Sized from
Distribution board to inverter	Pass-through load plus the battery charging current	220 V AC	The ladder below
Inverter to backup board	The backup load only	220 V AC	The ladder below
Battery bank to inverter	Many times the AC current	12, 24 or 48 V DC	Battery cable guide

The last row is why a 1 kVA UPS sits on a 2.5 mm² AC cable and a battery lead as thick as a thumb: 1000 ÷ 220 = 4.5 A on the AC side, but 1000 ÷ 12 = 83 A off a 12 V battery before losses. Same power, about one eighteenth of the voltage, so about eighteen times the current.

The AC ladder, by inverter rating

For a single-phase UPS or inverter in Pakistan, take the AC cable each side from the unit's VA rating divided by 220 V: 800–2000 VA is 3.6–9.1 A and runs in 2.5 mm² on a 16 A MCB, 3000 VA is 13.6 A and runs in 4 mm² on a 20 A MCB, and 5000 VA is 22.7 A and runs in 6 mm² on a 32 A MCB. Every row is three-core, because the backup supply has to carry its own earth.

Current = VA ÷ 220. Capacity is the two-loaded-conductor figure per BS 7671 reference method C (clipped direct), 30°C ambient, copper, PVC; stranding per IEC 60228. Take the input and output current from your own inverter's plate where it differs from the VA rating. Verify sizing with a licensed electrician for your installation.
Inverter rating	AC current at 220 V	Cable	Trade code	Capacity	MCB
800 VA	3.6 A	2.5 mm²	7/.029	27 A	16 A
1000 VA	4.5 A	2.5 mm²	7/.029	27 A	16 A
1500 VA	6.8 A	2.5 mm²	7/.029	27 A	16 A
2000 VA	9.1 A	2.5 mm²	7/.029	27 A	16 A
3000 VA	13.6 A	4 mm²	7/.036	36 A	20 A
5000 VA	22.7 A	6 mm²	7/.044	46 A	32 A
7500 VA	34.1 A	10 mm²	7/.052	63 A	40 A

Work a real one through. A 3000 VA hybrid inverter backing up two rooms: 3000 ÷ 220 = 13.6 A, so 4 mm² on a 20 A MCB. Over a 10 m run from the board to the inverter, 4 mm² drops 11 × 13.6 × 10 ÷ 1000 = 1.50 V. Hold the installation to 3% of 220 V — 6.6 V — and give the final circuit half of it, 3.3 V, since the submain has spent the rest; 1.50 V is comfortably inside that. Derate the table figures for conduit, bundling and summer ambient before you set the breaker: at a 0.75 correction, 4 mm² still holds 27 A against that 20 A MCB.

A backup supply must never be able to feed back into the utility side. Take the mains in and the backup out through a changeover switch or the inverter's own transfer relay, on a dedicated MCB, with the earth carried through on the third core and an RCD on the backup board. Current capacity also depends on how the cable is installed — derate for conduit, grouping and ambient temperature above 30°C. Have a licensed electrician confirm the size and the changeover arrangement for your unit — or start with the cable size calculator.

The cable for this job

Standard cable with black outer sheath cut back to show insulated stranded copper conductors

6MM² · 3 CORE · 450/750 V · CU CLASS 2

6mm 3 Core Standard Cable

Class 2 stranded copper, 7/1.04, PVC insulated and sheathed, 450/750 V, drawn on the Pilone line in Lahore. Rated 46 A on two loaded cores clipped direct at 30°C, 7.3 mV/A/m. The size for a 5 kVA inverter each side.

Factory-direct price

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Cable is priced off the day's copper rate, so we quote per metre and per coil on WhatsApp rather than publish a figure that goes stale. Send the metres and your city.

For the smaller ratings: 2.5mm 3 core flexible cable up to 2000 VA, 4mm 3 core cable at 3000 VA, and 10mm 3 core cable at 7500 VA.

Frequently asked

UPS ke liye kitne mm ka wire chahiye?

1000 se 2000 VA tak ke ghareloo UPS ke liye 2.5 mm² copper — trade code 7/.029 — 16 A MCB par. Current nikalne ka tareeqa seedha hai: VA ko 220 se taqseem karein, yani 1000 ÷ 220 = 4.5 amp. 3-core lein taake earth bhi sath jaye. Battery wala wire alag aur bohat mota hota hai.

Is the inverter cable the same as the battery cable?

No, and it is the mistake that costs the most. The AC runs each side of the inverter carry the VA rating divided by 220 V. The battery run carries the same power at 12, 24 or 48 V, so the current is many times higher — 1000 VA off a 12 V battery is about 83 A. Size that run in the battery cable guide, not from this table.

What size cable for a 5kVA solar inverter?

6 mm² copper on a 32 A MCB, three-core, on both AC runs. 5000 ÷ 220 = 22.7 A, and 6 mm² carries 46 A clipped direct at 30°C, so it keeps margin over the breaker after derating for conduit and summer heat. The PV strings and the battery bank are separate runs with their own sizes.

Does the backup circuit need its own MCB and a changeover?

Yes to both. The inverter feed gets a dedicated MCB at the main board, sized to the table above, and the backup circuits sit on their own board behind an RCD. The changeover switch, or the inverter's transfer relay, is what stops the backup supply reaching the utility side. Have a licensed electrician set it up.

Inverter cable at the factory rate

We draw the copper in Lahore and sell it at the day's rate — no dealer margin, and the line that made the coil answers the message. Send the inverter rating, the metres and your city: Punjab in 1–2 days, rest of Pakistan in 2–4.

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