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Work from the charger's current, not its kilowatts — and treat it as a load that runs at full current for hours.
A 7 kW single-phase charger draws 7000 ÷ 220 = 31.8 A. An 11 kW three-phase charger draws 11000 ÷ (1.732 × 400) = 15.9 A in each phase. That current is the starting point; the conductor size then depends on how the cable is installed, how hot it gets, how many circuits it is bundled with, and how far the charger sits from the board. There is no single answer to “what size cable for a 7 kW charger”, and anyone who gives you one without asking those questions is guessing. What this page gives you is the arithmetic and the variables, so the electrician who signs off the job is checking a number rather than inventing one.
Kilowatts sell chargers; amps size cables. The conversion is one line, and it is worth doing yourself because the same kilowatt figure means completely different currents on a single-phase and a three-phase supply. An 11 kW three-phase charger pulls less current per conductor than a 7 kW single-phase one, which surprises people who assume the bigger number needs the bigger cable.
| Charger | Supply | Current drawn | Arithmetic |
|---|---|---|---|
| 3.6 kW | Single phase 220 V | 16.4 A | 3600 ÷ 220 |
| 7 kW | Single phase 220 V | 31.8 A | 7000 ÷ 220 |
| 11 kW | Three phase 400 V | 15.9 A per phase | 11000 ÷ (1.732 × 400) |
| 22 kW | Three phase 400 V | 31.8 A per phase | 22000 ÷ (1.732 × 400) |
Most homes in Pakistan are on a single-phase 220 V connection, which caps a home charger at around 7 kW in practice. Three-phase is common in larger houses, plazas and anywhere with a commercial connection, and it is what makes 11 kW and 22 kW units possible. Check which you have before you choose a charger, not after — it is the single biggest constraint on the decision, and it is covered on what your supply needs before a charger.
Almost nothing else in a house behaves like a car charger. A geyser heats up and cuts out on its thermostat. An air conditioner cycles. A kettle runs for three minutes. A charger draws close to its full rated current continuously for four, six, sometimes ten hours, usually overnight when nobody is watching it and often in the hottest part of the year.
That matters because the tabulated current capacity of a cable assumes it can lose heat to its surroundings. A cable that never reaches steady state on a kettle circuit reaches it comfortably on a charger circuit. The result is that the derating factors most domestic wiring quietly gets away with ignoring — conduit, bunching, a hot roof void, a June afternoon in Lahore — are the factors that actually decide an EV circuit.
A charging session holds near-full current long enough for the cable, the conduit and the air around them to reach their final temperature.
Overnight charging means nobody notices a warm cable, a loose terminal or a cover that was never screwed back on.
On a single-phase domestic supply a 7 kW charger can be the largest single load in the house by some margin.
The table below is the tabulated starting point: what each size carries clipped direct in open air at 30°C. Read it as the best case. Every real installation takes something off these numbers, and on an EV circuit it takes more off than usual, for the reasons above.
| Size | Strands (class 2) | 2 loaded | 3 loaded | Voltage drop | Copper per core |
|---|---|---|---|---|---|
| 2.5 mm² | 7/0.67 | 27 A | 24 A | 18 mV/A/m | 22.2 kg/km |
| 4 mm² | 7/0.85 | 36 A | 32 A | 11 mV/A/m | 35.6 kg/km |
| 6 mm² | 7/1.04 | 46 A | 41 A | 7.3 mV/A/m | 53.3 kg/km |
| 10 mm² | 7/1.35 | 63 A | 57 A | 4.4 mV/A/m | 88.9 kg/km |
| 16 mm² | 7/1.70 | 85 A | 76 A | 2.8 mV/A/m | 142.2 kg/km |
Put the 31.8 A of a 7 kW single-phase charger against that table and you can see why the answer is not obvious. 4 mm² carries 36 A on paper, which clears 31.8 A with very little margin — and margin is exactly what a continuous load in a hot conduit spends. 6 mm² at 46 A leaves room for the correction factors to take their bite. Which one is correct for your installation depends on the route, and that is a calculation, not a preference.
Given the same charger and the same cable, these three change the size that is actually correct. None of them is optional, and all three tend to point the same way — upward.
Clipped to a wall in open air is the friendly case. Buried in a conduit, in a wall chase, or in insulation, the same cable sheds heat far more slowly and carries less.
The tables assume 30 degrees C. A Lahore roof void or an outside wall in June is well above that, and the correction is applied before the cable is chosen, not after.
A cable bundled with other loaded circuits is warmed by them. Grouping factors apply to the whole bunch, not just to the newest cable in it.
Then there is distance, which is a separate question with its own arithmetic: a cable can be comfortably large enough to carry the current and still drop too many volts over a long run. That is worked through on charger far from the board.
The cable is one part. An EV charge point is a dedicated circuit and needs the rest of it to match: its own way on the distribution board rather than a spur off something else, a protective device rated so the cable is protected, and an earthing arrangement the charger will accept. Many units also specify the type of residual current protection they need, because of the kind of fault current a vehicle charger can produce.
We are not going to tell you which device to fit. The charger manufacturer publishes what its unit requires, and those instructions carry more authority than any general guide — including this one. Take them to your electrician along with the cable calculation, and let the two be checked against each other. What we can tell you about is the copper: see 6mm cable, 4mm cable, and the cable price list for what the sizes cost at the factory rate.