AC Charging vs DC Charging
What’s the difference between AC and DC?
There are two ‘types’ of electricity supply: AC and DC. Here a list of comparison points to explain the differences:
- Used for charging of electric vehicles at various speeds.
- Alternating Current/Power
- Available on power grid
- Can be transmitted economically over long distances
- Converted to DC by the car
- Typically used for fast charging of electric vehicles.
- Direct Current/Power.
- Is constant
- Stored in batteries of portable electronic devices (e.g. mobile phones, electric vehicles)
The power that comes from the grid is always AC power.
When charging portable electronic devices (e.g. mobile phones, electric vehicles), the power needs to be converted from AC to DC. This is done by a converter.
In the case of day-to-day portable electronic devices (e.g. mobile phones), a converter is usually placed inside the plug.
In the case of electric vehicles, this converter is inside the car.
In the case of DC chargers (for fast charging of electric vehicles) this converter can be found inside the charger itself. In this case the converter inside the charger takes care of the conversion. As a result, DC chargers are usually larger (and more expensive).
Power always needs to be converted from AC to DC when charging an electric vehicle, the technical difference between AC charging and DC charging is whether the power gets converted outside or inside the vehicle.
Fast chargers for electric vehicles make use of DC charging; they convert the power before it enters the vehicle. After conversion, the power goes directly into the car battery, bypassing the car’s converter.
A DC installation requires a lot of power from the grid (around 125 A). This makes its costs (production, installation and operation) quite high, resulting in higher tariffs for charging. However, as it usually allows for much faster charging, it is the preferred charging method to quickly recharge during long-distance trips (for cars that support DC charging). This type of chargers is mostly found along highways, rather than at home or business locations.
This is the most common charging method for electric vehicles with a plug. When plugging an electric vehicle into a normal charge point, the power gets converted inside the vehicle, then moves into the car battery. Charging speeds depend on the output power of the chargepoint as well as the convertor’s capabilities to convert the power to DC.
The required power for AC chargers ranges between 16A (3.7 kWh) and 63A (43 kWh).
This charging method is most suitable for parking spots where the car will stay parked for 20 minutes or longer. Due to its lower costs (production, installation and operation) these are the more commonly found chargers. Also, due to these lower costs it is usually much cheaper to charge at AC chargers, making them more popular for general day to day charging.
Regardless of AC or DC, generally the costs (production, installation and operation) and therefore the charging tariffs will go up with increasing power of the chargepoint.
Note that this does not take into account the charging speed of your car. So if your car can not charge on high capacity, but you’re connected to a high output AC chargepoint (e.g. 43 kWh) you may pay a very high price for a low amount of energy.
Which one is better for my situation?
Ultimately, what’s better depends completely on the use case. If you’re in need of a quick recharge to continue your long-distance journey then you’ll usually choose DC charging (if your car supports it). For any other use case, AC charging will be the way to charge your car.
A general tip: match the charging capacity of your car with that of the charge point. Check our app for the average charging price per charge point.