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09/05/2022 News

kW, kVA, kWh... Better understand the electric mobility environment

You want to learn more about electric mobility (hereinafter “EV”) but you don’t know where to start? We don’t blame you, this world could seem a little bit difficult and confusing at first sight! If you already have a foot in the EV environment, you must have already seen different figures followed by different units… And now you are wondering how to understand what all these figures in kVA, kW, kWh mean?

TotalEnergies is here to help you understand better!

Before going any further, let’s define these units together:

  • kVA, acronym for kiloVoltAmpere, is a unit of electrical power. It represents the apparent power that can be delivered by a meter of a domestic installation.
  • kW, acronym for kiloWatt, is a unit of electrical power. It represents the active power of an electrical device at a given time, in other words, it represents the capacity to deliver an instantaneous quantity of energy.
  • kWh, acronym for kilowatt hour, represents the amount of energy consumed by an electronical device at a given time. If we refer to the EV environment, kWh represents the amount of energy charged in an electric vehicle battery.

Power units : kVA and kW

To get started, let’s take a closer look at the units that express the power during a charging session. You are maybe wondering what is the difference between kVA and kW, to give you more details, let’s focus on a charger itself.  

 

 

Scheme

 

 

We can distinguish the effective power (kW) to the apparent power (kVA) because the power is not transmitted the same way to the vehicle in both cases.

Just for a quick reminder, the battery of an electric vehicle can be charged only by direct current (DC).

Chargers delivering alternating current (AC) transmit alternating power directly to the electric vehicle. Then, this current is converted into direct current (DC) thanks to a charger integrated in the vehicle. The energy will then be stored in the vehicle’s battery to charge it. The Charge Point Operator (CPO), the one that operates chargers, do not have the possibility to measure the power transferred by the on-board charger installed in the vehicle to its battery. The CPO can only evaluate the power delivered by the charger that he operates. In this case, we can only calculate the supposed power delivered, thanks to collected data. Therefore, we can talk about apparent or theoretical power. The kVA is the unit that is used to measure this apparent power delivered by AC chargers.

 

Scheme

 

 

 

Chargers delivering direct current (DC) integrate the charger which allows to convert the alternating current into direct current. That’s why we are able to know the exact power which is delivered by the DC charger and received by the vehicle. In this case, we talk about effective power, which is expressed in kW.

However, the difference between effective power and apparent power is quite small . It is common to talk about kW even if EV drivers use AC chargers, even if theoretically, it is not accurate.

 

What about kWh ? 

As we already mentioned, kWh does not express electrical power, but rather the amount of energy delivered or consumed. In the EV environment, the amount of energy measured in kWh is stored in the battery of the electric vehicle. According to the size of the battery, the amount of energy stored can be more or less important. In fact, all vehicles don’t have the same battery capacity. It’s the battery capacity that will determine the autonomy of your electric vehicle and the number of kilometers it can recover when it is fully charged.

Before going any further, you should keep in mind that the formula to calculate the kWh value is :

[kW] x [h] = [kWh]

Imagine an EV driver who wants to stop to have lunch from 1pm to 2:30pm around a service station. The battery capacity of his/her  vehicle is 60 kWh  and is charged up to 20%. The EV driver decides to connect his/her  vehicle to an AC charger, delivering up to 22 kVA.

 

If he/she wants to estimate the amount of energy that his/her car can potentially recover by the end of the lunch break, here is the calculation he/she needs to make :  

22kVA x 1,5 (1h30) = 33 kWh

 

By the end of his/her break, the electric vehicle will have recovered 33 kWh, which means the battery will be charged up to approximately 78%. However, this number is an estimation because it is unusual that the power delivered by a charger reaches its maximum during a session.

To give you an idea, filling up 30 kWh allows you to drive for about 175 km.

 

To go a little bit further, let’s compare the battery capacity of objects of our daily life with electric vehicles’ battery.

 

  • Latest smartphone : 11,97 kWh
pexels-tyler-lastovich-719399.jpg

 

 

 

  • Daily energy consumption of a French household  : 12,5 kWh
pexels-scott-webb-1029599.jpg

 

  • Battery capacity of the Renault Zoé : 52 kWh
renault_zoe_-_insideevs.png

 

 

  • Battery capacity of an electric vehicle Long Range and Performance 2019/2020 : ~77 kWh Panasonic
pexels-matt-weissinger-11139552.jpg

 

 

To summarize 

Power units Fields of application Power conversion and use
kW - kiloWatt Direct Current (DC) Charger installed in a DC charger and that converts AC current into DC current before transferring it in an electric vehicle
kVA - kiloVoltAmpere Alternating Current (AC) Charger installed in an electric vehicle and that converts AC current transferred by the AC charger into DC current, before powering up the vehicle’s battery
Power units Definition Use
kWh – kilowatt hour Represents the amount of energy charged Stored in the battery of an electric vehicle

 

While a driver fills up his/her tank and buys liters of fuel, an EV driver power up his/her battery and buys kWh. TotalEnergies, as a Charge Point Operator, offers its customers different solutions to charge their electric vehicle. The Company operates chargers delivering several types of power in order to satisfy the needs of each EV drivers. If you don’t know which power you should use for your vehicle, have a look at how many kilometers can an electric vehicle recover ? 

Suitable for all types of electric vehicles, and available throughout Europe, the chargers operated by TotalEnergies can deliver power ranging from 3 kVA to 350 kW.

 

Sources : 

iphon.fr

lenergietoutcompris.fr