EV Home Charger Wiring Planner
Enter your home charger's rated current, system voltage and cable run length to get the correct breaker size, wire gauge in mm² and AWG, and voltage drop. Covers single-phase Type 2 chargers (3.7 to 7.4 kW) and three-phase installations (11 to 22 kW). All EV circuits are continuous loads and are sized at 125% of rated current per IEC 60364 and NEC.
Last updated: May 2026
Select a charger preset or enter current, voltage and cable run to size your circuit.
EV chargers are continuous loads: circuits are sized at 125% of rated current (IEC 60364 / NEC 210.20).
How the EV home charger wiring planner works
Every home EV charger is classified as a continuous load because it runs at full current for 3 or more hours per session. IEC 60364 and NEC 210.20 both require that the circuit breaker and cable be sized at 125% of the charger's rated current, not 100%. The planner applies this rule automatically and then checks two independent constraints: the cable must be large enough to carry the current without overheating (ampacity), and the cable must be large enough to keep the voltage drop within your chosen limit. The correct gauge satisfies whichever constraint is stricter.
Formulas used
| Output | Formula |
|---|---|
| Design current | Charger rated current (A) x 1.25 |
| Breaker size | Next standard IEC size at or above design current |
| Min. wire (single-phase) | 2 x rho x L x I_design / (V x drop%) |
| Min. wire (three-phase) | sqrt(3) x rho x L x I_design / (V x drop%) |
| Actual voltage drop | Phase factor x rho x L x I_rated / wire_area |
rho = 0.0172 ohm.mm²/m (copper) or 0.0282 ohm.mm²/m (aluminium). Phase factor = 2 for single-phase, sqrt(3) for three-phase.
Common charger wiring reference
| Charger | Current | Phase / Voltage | Design current | Breaker (IEC) | Min. wire Cu, 10 m, 3% |
|---|---|---|---|---|---|
| L1 US 1.9 kW | 16 A | Single / 120 V | 20 A | 20 A | 2.5 mm² (AWG 13) |
| EU 3.7 kW | 16 A | Single / 230 V | 20 A | 20 A | 2.5 mm² (AWG 13) |
| EU 7.4 kW | 32 A | Single / 230 V | 40 A | 40 A | 6 mm² (AWG 10) |
| UK 7.7 kW | 32 A | Single / 240 V | 40 A | 40 A | 6 mm² (AWG 10) |
| 3-phase 11 kW | 16 A/phase | Three / 400 V | 20 A | 20 A | 2.5 mm² (AWG 13) |
| 3-phase 22 kW | 32 A/phase | Three / 400 V | 40 A | 40 A | 6 mm² (AWG 10) |
Wire sizes shown for 10 m one-way run, copper, 3% voltage drop limit. Use the planner above for your actual run length.
Installation checklist
- Dedicated circuit: the EV charger must be the only load on its breaker and cable run.
- RCD/GFCI protection: IEC 60364-7-722 requires Type B RCD for all Mode 3 EV chargers; Type A is sufficient only where the charger has built-in DC fault detection.
- Earthing: a dedicated protective earth conductor must run with the circuit. Do not rely on conduit or building steel for earthing.
- Cable routing: avoid bundling the EV cable with other loaded cables in the same conduit or trunking without applying grouping de-rating factors.
- Cable entry: protect the cable at the consumer unit with a correctly rated gland or bushing. Secure every 400 mm (16 in) in free air or as required by local code.
- Sign-off: a fixed wiring installation for an EV charger must be inspected and certified by a qualified electrician in most jurisdictions.
Frequently Asked Questions
What size breaker do I need for a 7.4 kW home EV charger?
A 7.4 kW single-phase charger at 230 V draws 32 A continuously. The 125% continuous-load rule gives a design current of 40 A. The correct IEC breaker is the next standard size at or above 40 A, which is 40 A exactly. In practice many installers fit a 50 A breaker for a small margin, but 40 A is code-compliant if the cable is rated accordingly. For a 240 V UK installation the math is identical: 7680 W / 240 V = 32 A, design current 40 A, breaker 40 A.
What wire gauge is needed for a 22 kW three-phase EV charger?
A 22 kW three-phase charger at 400 V draws 22,000 / (sqrt(3) x 400) = 31.8 A per phase, rounded to 32 A rated. Design current at 125% = 40 A. Ampacity minimum: 6 mm² copper in conduit carries 40 A at 30 °C. For a 10 m run at 3% drop (400 V), the voltage-drop minimum is well below 1 mm², so ampacity governs. Use 6 mm² (AWG 10 equivalent) for most installations. For runs beyond 30 to 35 m, increase to 10 mm² to keep voltage drop inside the 3% limit.
Does the EV charger circuit need its own dedicated breaker?
Yes. An EV charger is a dedicated, continuous load and must have its own circuit breaker and cable from the consumer unit (distribution board). Sharing a circuit with other loads is not code-compliant and can cause nuisance tripping, voltage drop problems, and unsafe cable temperatures. The cable from the consumer unit to the charger must carry only the EV load.
How does cable run length affect the wire gauge I need?
Longer cable runs increase resistive voltage drop. For a 32 A charger at 230 V single-phase with 3% drop limit, the voltage-drop minimum for a 10 m run is about 2 mm² (well below the 6 mm² ampacity minimum, so ampacity governs). At 40 m, the voltage-drop minimum rises to about 7.9 mm², which exceeds 6 mm², so you would need 10 mm² to stay inside the drop limit. Enter your actual run length in the planner above for the precise threshold.
Is aluminium cable acceptable for a home EV charger circuit?
Aluminium is permitted by IEC 60364 for fixed wiring, but it is generally restricted to conductors 35 mm² and larger for branch circuits. For a typical 6 mm² EV charger circuit, copper is strongly preferred. Aluminium requires anti-oxidant compound at every termination, aluminium-rated connectors, and careful torque to prevent the cold-flow that causes loose connections over time. If aluminium is used, size at least one standard step larger than the copper equivalent, as aluminium carries roughly 78% of the same cross-section copper.
Next steps in this workflow
Breaker and wire sized: verify the drop across your actual run, then check your panel capacity.