How it works

Simple inputs → useful estimates for cost, miles, and time.

Calculator How it works About Privacy

Step 1: Energy added to the battery

SOC change

If your battery is B kWh and you charge from S% to T%, energy added to the battery is:

Formula
Energy to battery = B × (T − S) / 100

Example: 60 kWh battery from 20% to 80% → 60 × 0.60 = 36 kWh added to the battery.

Step 2: Account for charging losses

Energy from the wall

The wall supplies a bit more energy than the battery receives. If losses are L%:

Formula
Energy from wall = Energy to battery ÷ (1 − L/100)

Typical: AC home charging ~8–12%. DC fast charging can be lower, but varies.

Step 3: Cost

Tariff

Enter your electricity price in p/kWh. The calculator converts it into £/kWh and multiplies by energy from wall:

Formula
Cost (£) = Energy from wall (kWh) × Price (£/kWh)

If you choose “Add VAT”, the calculator adds 20% to the entered price (useful when comparing VAT-excluded figures).

Session time

AC vs DC

AC (Home) is approximated as near-constant power:

AC time
Time ≈ Energy from wall ÷ Charger kW

DC (Supercharger) slows near high SOC. The calculator uses a simple taper model to increase time at high SOC so 80% → 100% takes longer than you’d expect from constant power.

It’s still an estimate: exact taper depends on battery temperature, preconditioning, and vehicle limits.