EV Charger Calculator

Calculate the charging time of an electric car from any station: 230 V socket, 3.7–22 kW Wallbox, fast DC stations. Size the breaker, RCD (type A) and cable for a home charging station.

What the calculator computes

• Full charge time from a socket, Wallbox and fast station
• Charging current by phase (1-phase and 3-phase charging)
• Circuit breaker, type A RCD and cable section for a home charging station
• Check of remaining house power (whether charging exceeds the allocated capacity)
• Charging cost by tariff (day/night)
• Charging losses (charger efficiency 85–90%)

How to calculate charging time

Charging time: t = E_battery × (SoC_final − SoC_initial) / (P_charge × η), where E is the battery capacity (kWh), P is the charging station power (kW), η is the efficiency of the onboard charger (0.88–0.92 for AC charging, 0.93–0.97 for DC).

Example: Tesla Model Y (60 kWh), charging 20→80% = 60 × 0.6 = 36 kWh. From an 11 kW Wallbox (3-phase, η = 0.9): t = 36 / (11 × 0.9) = 3.6 hours. From a 2.3 kW socket: t = 36 / (2.3 × 0.9) = 17.4 hours.

Charging current: I = P / (U × phases). For 1-phase 230 V: 7.4 kW → 32 A; for 3-phase 400 V: 11 kW → 16 A per phase, 22 kW → 32 A per phase.

Regulatory requirements for a home charging station

EVSE installation is regulated by IEC 61851 (conductive charging), IEC 60364-7-722 (supply of electric vehicles), and national rules (UK: BS 7671 Section 722; Germany: VDE 0100-722; US: NEC 625). Requirements:

— a separate line from the board to the charging station with its own breaker;

— RCD type A or B (DC leakage) 30 mA is mandatory;

— cable with flame-retardant insulation, section per design current: 3.7 kW/16 A — 2.5 mm²; 7.4 kW/32 A — 6 mm²; 11 kW/16 A (3-ph) — 5×2.5 mm²; 22 kW/32 A (3-ph) — 5×6 mm²;

— earthing per the national system (TN-C-S in most of Europe);

— in many EU countries, domestic wallboxes above 3.7 kW require notification to the DSO, and smart charging (EN 50491-12) is mandatory in some markets.

Connectors: Type 2 (Mennekes) for AC and CCS Combo 2 for DC in Europe.

Charging speed table

How to use the calculator

1. Select the EV model from the list or enter the battery capacity manually.
2. Specify the state of charge before and after (20→80% by default — manufacturers' recommendation).
3. Select the charging type: socket, 3.7/7.4/11/22 kW Wallbox or fast DC station.
4. For a home station, specify the house allocated power — the calculator will check the margin.
5. Press «Calculate» — charging time, current, breaker, RCD, cable, cost.

Common mistakes

• Charging 7.4 kW from a socket — a standard socket handles 16 A max; 32 A requires a separate line.
• RCD type AC instead of A — chargers generate pulsed DC leakage current that type AC cannot detect.
• Two-phase load in a three-phase network — phase imbalance.
• Not accounting for charger efficiency — real time is 10–15% more than the «pure» calculation.
• Charging to 100% daily — accelerated battery degradation; optimal 20–80%.

EV charging FAQ

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