EV Charging explained

Answering your questions about EV charging and storage 

As we transform from Petrol and Diesel cars over to Electric cars we are finding it harder to work out all the jargon.

What is KW & KWh and how do they differ. We have tried to answer your questions in plain English below so you can better understand what it's all about. 

The 2 key areas, like a petrol or diesel car are power and storage. With petrol and diesel cars we refer to brake horsepower (BHP) to determine the power of the vehicle and the fuel tank is the storage.

When we work out the distance a Petrol or diesel car will travel we  look at the published miles per gallon (MPG) and the capacity of the fuel tank. this is the same with an electric car except the Power is KiloWatts (KW) and the storage is KiloWatt Hour (KWH)

So to summarise: 

KW = Power

KWH = Capacity

EV power


KW is the power an EV has. The larger the KW the more powerful the car. Think of it like a 1.0ltr Fiesta against a V8 Mercedes.

Petrol/ Diesel cars are measured by Brake Horsepower (BHP), EV’s are measured by KW although you do see BHP figures used, this is because we can relate to these figures better.

See the Examples below of the Polestar 2 with different motor configurations

Polestar 2 Standard Range single motor 200KW - 0-60 in 6.4 seconds and equivalent to 272bhp - Range 322 miles

Polestar 2 Long Range single motor 221KW - 0-60 in 6.2 seconds and equivalent to 300bhp - Range 406 miles

Polestar 2 Long Range duel motor 310KW - 0-60 in 4.5 seconds and equivalent to 421bhp - Range 367 miles

The KW doesn’t determine the distance an EV can travel as a performance EV could have a smaller KWh capacity and/ or with that extra power it could also drain the battery quicker. It’s the same if you put your foot to the floor in a petrol/ diesel car you will use more fuel.

EV barry charging


KWH is the capacity. Think of it like the fuel tank in a petrol/ diesel car.

So in a Petrol or Diesel car that has a 72 litres fuel tank, this will allow you to travel 633 miles based on 40mpg (72lts / 4.546 (converted to Gallons) x 40mpg.

In an EV car KWh will determine how far you can travel. For example, the Nissan Leaf has a 39KWh battery and can travel 168 miles on a full charge whereas a Polestar 3 Long Range has an 82KWh battery and can travel 406 miles on a full charge.

How to work out the cost of charging your EV car. 

Size of EV’s battery pack (KWh) × electricity cost of your supplier (in pence per kWh) 

We’ll use the Atto 3 as an example.

It’s powered by a 60 kWh battery pack. [Row 4] x Cost per kWh of 25p [Row 6] So, 60KWh × £0.25p = £15 is the cost of charging the car from empty to full at home.

Here are some examples of popular cars.

The cheapest rates at the moment, if charging overnight, are around 8p per KWh. If you charge on the road the price will vary depending on the size of the charger and can range from 36 ppKw to 65 ppKW

We have based the prices below (both home and on the road) on 25p per KWh. 















Pence KWH

Cost to charge

Cost per mile

Nissan Leaf








Tesla Model 3 RWD 








Atto 3








BMW I4 35








Polestar 2 LR SM









What's the cost per mile of my EV

The next cost you will want to know is how much does it cost to run per mile. 

For this you need to know the cost to charge your vehicle [row 6] / the range of the vehicle (or the range that you achieve) 

We’ll use the Atto 3 as an example again.

It’s cost £15 to charge up [Row 6] / Range of the vehicle [Row 1] So, £15 / 260p = £0.059ppm is the cost per mile

EV Charging

Charging an EV Car

There are different charging rates from a 3pin plug to 300KWh super chargers.

Each car will have its own capacity with some cars restricted to how much charge they can take. See the user manual for this information.

Most home installations will have a 7.5KW unit and this will be the maximum charge rate.

This means when you charge your car it will add 7.5Kw of energy into your car every hour. So if you have a 60KWh battery capacity it will take 8hrs to charge from empty to full.

Be aware its unlikely that you will be charging your car at the maximum rate and it will be your supply that dictates the amount of energy produced. 

Charging at home

You can charge your car using your domestic 3 Pin 13amp Plug. This will give you the equivalent of around 3KW

A home Charger unit will give you a max 7.5Kw This is because most homes only have single phase electrics.

SAFETY NOTE: If you do charge your car from a 3 Pin plug and you are using an extension lead make sure to uncoil the extension lead completely and don’t leave it wound up.

A coiled lead will generate heat and could cause a fire.

Make sure you have a good circuit breaker in place.

Charging at work

At some workplaces you will have a 3 phase supply and therefore you may (depending on supply) install a 22kW charger which will allow you to charge your vehicle quicker. 

How long it takes to charge your EV

The table shows how long it will take to charge a 50KW car using the different charging times depending on the type of charger used.

Not all vehicles can except the higher charging rates so please refer to your manufacturer handbook.


Charging times



Max KW

Time to change 50KWh battery

3 Pin Plug



16.6 hrs

7.5KW home changer



6.6 hrs


3 Phase


2.27 hrs


3 Phase


1 hr


3 Phase


40 mins


3 Phase


30 mins


Find the best Electricity deals

There are a number of comparison sites like smarthomecharge and rightcharge

While out on the road, many cars will have the charging points on their sat nav maps or you can use sites like Zap-map


Want to know how EV's could benefit you and your company and would like some helpful free advice, then call us on 01242 500 007 or complete the form below.