EV Charging Time Calculator

This calculator estimates how long it takes to charge an electric vehicle based on your battery size, current charge level, target charge level and charger power.

Basic formula

Charging time = Energy needed / Charger power

Where: Energy needed = Battery capacity × (Target% - Current%) / 100

Charging curve (rapid chargers)

DC rapid chargers (50 kW and above) cannot maintain full power above approximately 80% state of charge. The battery management system reduces power to protect cell health. This calculator accounts for this by splitting the charge into two phases:

• Below 80%: Full rated charger power
• Above 80%: Reduced to ~35% of rated power

Charging efficiency

Not all energy from the grid reaches the battery. AC chargers (3-pin, 7 kW, 22 kW) have approximately 90% efficiency — 10% is lost as heat in the onboard charger and cables. DC chargers are slightly more efficient at ~95%. The calculator applies these losses to both the charging time and the cost, because your meter records the energy drawn from the grid (the higher figure), not the energy delivered to the battery.

Charger types

• 3-pin plug: 2.3 kW (10A) — emergency/occasional use only
• 7 kW home charger: Single-phase AC — the UK standard for home charging
• 22 kW: Three-phase AC — workplaces and destination chargers
• 50 kW rapid: DC CCS/CHAdeMO — motorway services, public hubs
• 150 kW ultra-rapid: DC CCS — newest public rapid chargers

Cost calculation

Cost = Grid energy drawn × Electricity rate, where grid energy = energy delivered to the battery ÷ charging efficiency. Home charging at the Ofgem cap costs 26.11p/kWh (1 Jul–30 Sep 2026); off-peak EV tariffs can reduce this to 7–10p/kWh. The Ofgem cap is reset every quarter, so confirm the current rate before relying on a figure.