EV Charger Installation: How Many Amps Does a 7kW or 22kW Charger Need?

When you pick a 7 kW or 22 kW EV charger, installers don’t size the circuit from “kW” alone. They care about amps, and amps depend on your supply voltage, whether the circuit is single-phase or three-phase, and (for AC) an optional power factor correction that is usually very close to 1 for modern chargers.

The shortcut:

• Single-phase (and DC math): I = P ÷ (V × PF) where P is in watts (kW × 1,000).
• Three-phase AC (line-to-line voltage V_L-L): I = P ÷ (√3 × V_L-L × PF) — often written with √3 ≈ 1.732.

Use PF ≈ 1 for a first-pass EV charger estimate unless your manufacturer specifies otherwise.

Our Kilowatts to Amps Calculator (see the tool section at the end of this post) runs the same math with your exact kW, volts, and phase so you can line up your assumptions before you review a quote.

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Why a 7 kW charger and a 22 kW charger behave differently

7 kW (single-phase) is the common home install in many regions: it’s enough for overnight charging on a typical domestic supply without jumping to industrial three-phase wiring.

22 kW is usually a three-phase wallbox. Pulling 22 kW from single-phase 230 V would need on the order of 22000 ÷ 230 ≈ 96 A before any derating — impractical on most homes. That is why 22 kW equipment is associated with 400 V (or similar) three-phase supplies in many European installations.

Always confirm the nameplate and the install manual: “7 kW” can refer to delivered power to the vehicle, input limits, or a rounded marketing figure.

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Quick estimates (PF = 1)

Round numbers you can sanity-check in your head or plug into the tool:

7 kW → single-phase examples

• 230 V: 7,000 ÷ 230 → about 30 A
• 240 V: 7,000 ÷ 240 → about 29 A

22 kW → three-phase example (400 V line-to-line)

• I = 22,000 ÷ (1.732 × 400) → about 32 A per line

If your site voltage differs (for example 208 V line-to-line in some North American commercial panels), the same kW produces a higher current. That is why quoting amps without voltage is incomplete.

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Breakers, “continuous” loads, and why your circuit might be rated higher than the math above

Physics gives you running current; permits and panel schedules add margin. Many jurisdictions treat EV supply equipment as a continuous load for wiring and overcurrent protection, which often means the breaker and conductors are larger than the headline amp figure alone suggests.

Rules vary by country and code cycle. Treat this article as planning context, not a substitute for a qualified electrician or your local code.

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Before you approve a quote

Checklist:

• Exact model and maximum input kW / amps from the datasheet
• Nominal voltage at your meter / panel (230 V, 240 V, 208 V, 400 V line-to-line, etc.)
• Single-phase vs three-phase service
• Whether the installer sized for continuous load and voltage drop on the run (long cable runs matter)

Recompute amps for your numbers with the calculator, then compare to the proposal — discrepancies are worth a question, not an argument.

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Use the Tooladex Kilowatts to Amps Calculator — switch between DC-style single-phase and three-phase line-to-line modes, adjust power factor if needed, and match what your wallbox documentation assumes.