What power do I need to charge my electric vehicle?

This article will explain the different types of power and how that affects the speed at which you can charge your electric vehicle (EV).

What are the different types of electricity?

There are two different types of charging, AC (Alternating Current) and DC (Direct Current). Your home electricity supply is AC.

AC charging is generally used at home, and DC charging is used in the street, in offices and often at service stations.

Why am I limited in how quickly I can charge my EV at home?

The electricity in a car battery is DC. When you use a home EV charger, AC electricity is sent to the car from your home mains supply, and the car’s OBC (On-Board Charger) converts the AC to DC, which charges the electric vehicle battery.

This limits the speed at which the car battery charges because different electric vehicles have OBCs with different capabilities. For example, a Jaguar I-PACE has an OBC rated 7.4kW. This means the maximum you can charge in AC is 7.4kW. Even if your home charge point is capable of charging at 22kW, the I-PACE can only charge at 7.4kW. A Renault Zoe can charge at 22kW.

On a DC charger (in offices and public charge points), the charge point converts the AC into DC before it reaches the car battery. This means the car doesn’t need the OBC to convert the electricity from AC to DC, so it can charge a lot faster than on a home charge point. A Jaguar I-PACE on DC charge can charge up to 100kW. A Tesla Model X can charge up to 145kW. This type of charging is called rapid charging.

Why don’t all EV Charge at a high rate on home charging?

There are a number of reasons why different models of electric vehicles charge at different rates. These include the cost of OBCs, the available space for the battery, and the faster you charge your EV, the more damage is done to the battery.

As an example, a new Tesla Model X is advertised as having a 100kW capacity, but it actually has a bigger battery than this. The software doesn’t allow you to use the last 10% at first, but over time it allows you to use more and more of the battery. This is how Tesla guarantees the battery and the car over eight years, by letting you use more of the battery over time. The battery does go down in performance but the software lets you use more of it.

Why can’t I have DC charging at home?

If you can charge your EV much faster on a public charge point because the charge point converts the AC electricity to DC before it reaches the vehicle, why can’t you have DC charging at home and so enjoy higher charging speeds?

There are a number of reasons for this:

1. You have limited power at home. You are limited by the amount of power in your home. Typically a home in the UK has between 60 and 100 amp fuse on a single-phase supply. If you have a 60 amp fuse, which many older properties have, this can be upgraded to a 100 amp fuse by UK power networks free of charge. You also can’t use more than 50% of your power for charging at home because you have other appliances which are also using the power supply, so you could not charge your car at 100kW with your home power supply.

2. DC charge points are very expensive. A charge point – otherwise called an inverter – is very expensive for DC charging. A 20kW DC charger starts from around £8000, making this out of the price range for most people seeking a home charge point.

3. You need a three-phase power supply to charge above 7kW. Most UK residential properties use a single-phase power supply, which means most home charge points charge at either 3.7kW or 7kW. For the difference between single-phase and three-phase AC charging, see the explanation below.

What is the difference between single-phase and three-phase electricity supply?

AC power supply is categorised into single-phase and three-phase. In a single-phase supply, the power flows through a single conductor. The power in a three-phase supply flows through three conductors, meaning three-phase has a higher capacity for power transfer than a single phase. Most industrial and business settings use three-phase, whereas most UK homes use single-phase because home appliances require less power.

A three-phase supply has the facility to run much higher power loads than a single-phase supply. The maximum an EV home charge point can charge at is 7kW because most UK homes use a single-phase supply.

Three-phase AC charging can charge up to 22kW, but it is expensive to upgrade your home supply from single-phase to three-phase. The cost varies depending on your local electricity infrastructure, and can be between £1000 up to £500,000!

How can I check whether I have single-phase or three-phase in my home?

You can use these pictures to diagnose whether you have a single-phase or three-phase supply.

Single-Phase Electricity Supply

Three-Phase Electricity Supply

Why get a home charge point that can charge a 22kW if my OBC can’t charge at that rate?

At this point in time, very few cars can do a full 22kW on AC, but moving forwards, car manufacturers are offering more and more powerful OBCs, so potentially if you are future-proofing a product, getting something that can charge at 22kW is probably beneficial because you will be able to use it in years to come.

What types of charging plugs are there for EVs?

There are different types of charging plugs for EVs. These are known as Type 1 and Type 2. Type 1 is used in American and Japanese electric vehicles, and Type 2 is used in European EVs.

What types of connectors are there?

For AC connectors:

UK 3-pin (BS 1363)
Industrial Commando (IEC 60309)
American Type 1 (SAE J1772)
European Type 2 (Mennekes, IEC 62196)

For DC connectors:

European Combined Charging System (CCS or ‘Combo’)
Japanese JEVS (CHAdeMO)
Tesla’s proprietary supercharger connector

Which socket should I use?

The vehicle’s inlet port and the charger type will determine which socket you use. Rapid chargers use CHAdeMO, CCS or Type 2 connectors. Fast and slow units (such as a home charge point) normally use Type 2, Type 1, Commando or 3-pin plug outlets.

European electric vehicles (such as Audi, BMW, Renault, Mercedes, VW, and Volvo) usually have Type 2 inlets and the CCS rapid standard. Nissan and Mitsubishi manufacturers tend to use a Type 1 connector and CHAdeMO inlet. The Hyundai Ioniq Electric and Toyota Prius Plug-In use Type 2 connectors.