EV Charging Time Calculator
Enter battery capacity, charger power, start and target state of charge, and charging efficiency. The calculator instantly estimates how long the session will take, splitting the result into the constant-power stage below 80 % SoC and the tapered constant-voltage stage above 80 % (DC fast charging only). Defaults to 60 kWh / 7.4 kW / 20 → 80 % / 90 % efficient, all freely adjustable, with quick presets for common chargers.
Common scenarios
Enter a valid battery size, charger power, start/target SoC (target ≥ start) and 50–100 % efficiency.
Estimated charging time
—
—
- Constant power (< 80 %)
- —
- Tapered (≥ 80 %)
- —
Energy and average power
- Into the battery
- — kWh
- Drawn from the grid
- — kWh
- Average power
- — kW
Formula
Energy to battery = capacity × (target% − start%) / 100 Energy from grid = energy_to_battery / efficiency AC time = energy / (charger_kW × efficiency) DC below 80 %: same as AC DC ≥ 80 % segment: segment_energy / (charger_kW × efficiency × 0.5)
- · Use the smaller of the EV’s on-board charger (OBC) rating and the connector output. An 11 kW OBC plugged into a 22 kW post still draws only 11 kW; a 7.4 kW OBC happens to match a typical 32 A single-phase home wallbox.
- · AC charging (single-phase 1.4–7.4 kW or three-phase 11/22 kW) is OBC-limited and the power stays essentially flat for the entire session — no taper above 80 %.
- · DC fast charging (CCS, CHAdeMO, NACS DCFC, Tesla Supercharger) transitions from constant current (CC, roughly 0–80 % SoC) to constant voltage (CV, 80–100 %), at which point the BMS reduces current to protect the cells. This tool approximates the 80–100 % segment with 0.5 × peak power, matching average charge-curve data published by Fastned, A Better Routeplanner and the P3 Charging Index across major EV models.
- · Wall-to-battery efficiency runs from 85–90 % for AC level 2 to 92–95 % for DC fast charging. Cold weather and hot OBCs drop it further. The default 90 % is a reasonable mid-point.
- · The model is good enough for planning (road-trip stops, electricity-bill estimates). Actual time depends on cell temperature, pre-conditioning, the specific SoC curve, dynamic load management, other cars sharing the cabinet and station-side derating — expect ±10–25 % swing in real life.
- · References: US DOE Alternative Fuels Data Center “EV Charging 101”; SAE J1772 / IEC 61851 charging levels; Fastned public charging-curve datasets; Tesla Owner’s Manual on Supercharger taper above 80 % SoC.
Frequently asked
Why does 80 → 100 % take so long compared to 0 → 80 %?
Lithium-ion packs are managed cell-by-cell to stay within voltage limits. Below ~80 % SoC the pack accepts current at full charger power (the CC stage). Above 80 % the cells are near their upper voltage and the BMS smoothly reduces current to hold voltage steady (the CV stage), so average power drops to roughly half of peak. As a result the final 20 % often takes about as long as the first 60 %. The road-trip rule of thumb is to leave at 80 %, not 100 %. AC charging stays flat because the on-board charger already limits power well below the battery’s acceptance rate — there’s nothing for the BMS to throttle.
How long does a standard 220 V / 13 A wall outlet (~2.4 kW) take?
Pick the "Home 3-pin" preset (~1.8–3 kW, depending on whether the breaker allows 10 or 13 A continuous) and enter your battery size. For a 60 kWh pack, 20 → 100 %, 88 % efficient: 48 kWh into the battery, 54.5 kWh off the grid, time = 48 / (2.4 × 0.88) ≈ 22.7 hours — i.e. two overnight sessions. A single-phase 32 A wallbox at 7.4 kW is the practical sweet spot for home charging (same scenario: about 7 hours, one overnight). If you can run three-phase 11 kW to the garage, even better.
Why isn’t my car drawing the full 350 kW from an ultra-rapid charger?
Two things have to line up: (1) your car must run an 800 V architecture (Porsche Taycan, Hyundai Ioniq 5/6, Kia EV6, Lucid Air, Audi e-tron GT and a handful of others). 400 V cars top out around 250 kW even on a 350 kW post; (2) the pack must be pre-conditioned to ~30–40 °C, which most cars only do when you set the charger as a navigation destination. Even with both in place, the curve still tapers sharply once you’re past 60–70 % SoC. This tool models the 80 %+ segment with 0.5 × peak; in practice low-SoC charging can be at or near peak briefly, while higher-SoC tapers drop faster. Apps such as PlugShare, ABRP and A Better Routeplanner show the actual measured curve for your specific car.
Where do the 10 % losses go and should I budget them into my bill?
The 10 % goes into: (1) AC-to-DC conversion losses in the on-board charger (5–10 % is typical); (2) I²R heating in the battery itself; (3) the cooling pump and fans running during charging; (4) cable and connector resistive losses. In cold weather (< 5 °C) cars also draw power to pre-heat the pack, and AC efficiency can drop below 75 %. Your utility bill measures whatever enters your meter, so this tool reports both energy into the battery (which sets your driving range) and energy drawn from the grid (which sets the bill). Multiply the grid figure by your electricity tariff to budget the real cost.
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