How the EV Charger Calculator Works

Enter your battery capacity, charger power and your electricity rate. The calculator returns charging time, cost of charge and effective pence per mile for your car's efficiency.

The core formula, charging time in hours = battery capacity in kWh ÷ charger power in kW. A 60kWh battery on a 7kW home wallbox takes roughly 8.5 hours from empty, which is precisely why 7kW became UK home standard, it fills almost any EV overnight. Real charging adds around 10 percent for losses and rapid charging slows sharply above 80 percent as car protects its battery, which is why public rapid times are quoted to 80 rather than 100 percent.

Charger Speeds Compared

Each charger type has a natural role:

• 3 pin plug, 2.3kW: 24 to 30 hours for a full charge, emergency use only
• Home wallbox, 7kW: 6 to 10 hours, adding 25 to 30 miles of range per hour
• Three phase, 22kW: rare at home since it needs a three phase supply few houses have
• Public rapid, 50kW: 80 percent in 30 to 40 minutes
• Ultra rapid, 150kW+: 80 percent in 15 to 25 minutes, where the car's own limit usually decides the speed

One detail that catches new owners, your car's onboard charger caps AC speed. A car with a 7kW onboard limit charges at 7kW even on a 22kW post, so slower of charger and car always wins.

What Charging Actually Costs

Tariff choice moves cost more than any other decision. On a standard rate of around 26p per kWh, filling a 60kWh battery costs roughly £15. On a dedicated EV tariff with an overnight window around 7p, the same charge costs about £4, under 2p per mile. Public charging runs other way, around 50p per kWh on slower public units and 60 to 80p on rapids, which can make a motorway top up cost more per mile than petrol.

The arithmetic across a year is stark. A typical driver covering 10,000 miles uses roughly 2,500kWh of charging, which is about £650 on a standard rate but £175 on an off peak EV tariff. That £450 to £500 annual saving is why a smart charger paired with an EV tariff pays for itself faster than any other EV accessory and most of these tariffs require exactly that pairing, a smart charger scheduling charge into cheap window automatically.

Installation Costs and the Grant

A 7kW smart wallbox typically costs £900 to £1,600 supplied and fitted, with a half day installation covering the unit, cabling, protection and certification. Long cable runs add £100 to £300 and a consumer unit upgrade, where needed, £300 to £800. Installation is notifiable electrical work, so use an OZEV approved installer who handles DNO notification and paperwork.

On grants, position often surprises people, homeowners with driveways are no longer eligible. The EV chargepoint grant, worth up to £500 since April 2026, applies to renters and flat owner occupiers with off street parking, with a separate scheme for landlords. If you qualify, installer applies it as a discount on invoice.

Getting More From the Setup

Two pairings multiply value of a home charger. Solar owners can fit a charger with a solar divert mode that trickles surplus generation into the car, cutting summer charging costs to nearly nothing. And since most EV tariffs open their cheap window to the whole house, running dishwasher and washing machine overnight extends saving beyond car. Tethered chargers, with cable attached, win on daily convenience, untethered socketed units look tidier and let you upgrade cables later. For dark winter mornings, a charger with load balancing stops the car and the electric shower fighting over the main fuse.