Electrical circuit breakers in the "on" position on a panel for charging electric vehicles.

What power do I need to charge my EV?

What Power Do I need to Charge my EV?

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.

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?

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 200 amp by an electrician in many cases. 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 $12,000, 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 US residential properties utilize single-phase power supply, which means most home charge points charge at either 3.7kW or 7kW.   An electrician can upgrade your panel as neccesary.

Why Get a 22Kw Charger if I 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.

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