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. If you are still choosing a charger, the cost and range tools in the EV & energy hub help you size the charging speed before you plan the wiring.
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.
The home charger is where the EV cost story starts
The house sets a ceiling on every number that comes after this page. Before you know what a charge costs, how long it takes, or whether a trip is feasible, you need to know what your consumer unit can actually deliver to a wallbox. That answer cascades through each tool in the sequence below:
- You are here: size the circuit before you choose the charger. Your consumer unit, available phases and cable run determine which charger power level is physically possible. For most Dutch and European households, 7.4 kW on a single 32 A phase is the practical ceiling without grid reinforcement. Three-phase 11 kW or 22 kW is technically cleaner wiring, but the extra install cost rarely pays back at home where the car sits overnight and a slower rate fills the battery just as reliably.
- See how long a charge takes. The power level this page gives you is the direct input to the EV charging time calculator, which models the taper curve above 80% and compares overnight versus rapid sessions.
- Price the charge session. Energy added times your home tariff. The EV charging cost calculator takes your battery size and the rate your wallbox runs at.
- Turn cost into cost per kilometre. The EV range and cost calculator divides energy by your real-world consumption so you can compare directly against petrol.
- Compare a full year against petrol. The EV vs petrol calculator puts your annual distance, home tariff and pump price into one number.
- Check a specific journey. The EV trip planner checks whether your range covers a route or whether a stop is needed.
- Lower the tariff by generating your own power. The solar panels for EV charging calculator sizes an array against your daily kilometres, which is the one move that reduces the tariff you enter in step 3.
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.
Can I share the EV charger circuit with the garage sockets or garden lights?
No. A Mode 3 wallbox is classified as a continuous load under IEC 60364-7-722 and must have its own circuit breaker and cable from the consumer unit, carrying only the EV load. Adding garage sockets or any other load to the same breaker is not code-compliant: the combined current can exceed the breaker rating during a charging session, and the cable temperature will exceed its rating well before the breaker trips. Run a separate circuit for the wallbox, even if it means pulling a second cable to the garage.
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.
Methodology and sources
This planner sizes the breaker and cable for a home EV charging circuit. It treats every charger as a continuous load, applies the 125% design-current rule, then sizes the conductor to satisfy whichever is stricter: thermal ampacity or your chosen voltage-drop limit.
- Method: Design current = rated current (A) × 1.25. Voltage-drop minimum cross-section = phase factor × rho × L × I_design / (V × drop%), with phase factor 2 for single-phase and √3 for three-phase. Actual drop = phase factor × rho × L × I_rated / wire area. The recommended size is the larger of the voltage-drop and ampacity minimums; the breaker is the next standard size at or above the design current.
- Standards and sources: IEC 60364 and NEC Article 210.20 (continuous-load 125% rule and breaker sizing), IEC 60364-5-52 (conductor ampacity reference), and IEC 60364-7-722 (EV charging installations, RCD requirements). Resistivity rho = 0.0172 ohm·mm²/m copper and 0.0282 ohm·mm²/m aluminium.
- Assumptions and limits: Ampacity figures assume roughly 30 °C ambient and a single circuit; no grouping or thermal-insulation de-rating is applied. The voltage drop uses the one-way run length you enter. A real install must add de-rating for bundling, insulation and high ambient temperature, plus the correct RCD type and a dedicated protective earth.
Reviewed and maintained by Rick Oosterling, who builds and wires 12 V, solar and EV systems hands-on. Last reviewed: June 2026. This is a planning aid, not a substitute for a qualified electrician or your local wiring and building code: a fixed EV charger circuit must be designed, installed and certified by a qualified professional.
Next steps in this workflow
Breaker and wire sized: verify the drop across your actual run, then check your panel capacity.