11 kW or 22 kW wall box?

4 reasons why an 11 kW wallbox is sufficient

August 22, 2022

How many kilowatts (kW) should a wall charging station have for charging at home? You may be asking yourself this question if you're about to purchase a wallbox to charge your electric car or plug-in hybrid. Maybe you think to yourself, "faster is better." But when it comes to the electric charging station in your driveway or garage at home, charging power plays only a minor role. But why?

Hardly any car can charge AC faster than 11 kW

The fastest that is realistically possible when charging at home is 22 kilowatts (kW). Yes, some time ago there were models that could handle AC charging at 43 kW, but this charging power no longer plays a role today. Many wallboxes can handle a maximum of 11 kW, some 22 kW. Now 22 kW is twice as much as 11 kW. But charging always takes two: wallbox and car. Your car may be able to charge quickly, but that refers to fast charging with direct current (DC) on highways and the like.

The charging speeds of up to 300 kW mentioned in advertising sound great, but you shouldn't let that fool you. At home, your electric car charges with alternating current (AC). Alternating current must first be converted into direct current by the car. With DC charging, on the other hand, direct current flows directly into the battery of your electric car, which stores it as direct current without the need for conversion. The cable also differs: for AC charging, the Type 2 plug is used, while DC charging requires the CCS plug (Combined Charging System), which is an extended version of Type 2 with two additional power contacts for fast charging.

Hardly any electric car can charge AC at 22 kW. Currently, only the expensive models from German premium manufacturers and smaller city runabouts can do this: Audi e-tron, Porsche Taycan and Mercedes EQS - where the additional weight of a larger AC charger is hardly significant - as well as Renault Twingo, Renault ZOE and Smart Fortwo, which - with the exception of Renault ZOE - do not have a DC charging option at all.

Charging with 11 kW is more gentle on the battery than with 22 kW

Charging an electric car at 22 kW instead of 11 kW is undoubtedly faster:

  • For example, a battery with just under 95 kWh, such as the one installed in the e-tron 55, needs only 6:55 h with 22 kW instead of 13:50 h with 11 kW.
  • The 83.7 kWh battery in the Porsche Taycan charges from 0 to 100% in 6:05 h at 22 kW. At 11 kW, the charging time increases to 12:10 h.
  • The huge 107.8 kWh battery of the Mercedes EQS needs 7:50 h to fully charge at 22 kW. With 11 kW, you need 15:41 h.
  • With a 52 kW battery, as found in the Renault ZOE, the charging time is reduced from 7:34 h to 3:47 h at 22 kW.
  • The Smart Fortwo with its 17.6 kWh battery charges from 0 to 100 % in 1:17 h at 22 kW. At 11 kW, it takes 2:34 h.
(All charging times refer to charging from 0 to 100%. Since it is common practice to charge from 20 to 80 %, shorter charging times can be expected in everyday life at both 22 kW and 11 kW).

Even if you have a 22 kW charging capable car, you should think carefully about whether you always want to charge at 22 kW, or only when you really have to. Because the higher the charging speed, the greater the load on the battery. This rule also applies to comparably low charging powers such as 11 and 22 kW. In the long run, regular charging with 22 kW would wear out the battery more than with 11 kW. So if you are particularly concerned about the battery health of your electric car, you should charge more slowly if possible.

Less approval effort for 11-kW wall boxes

If your car supports 22 kW charging, you face the next hurdle: A 22 kW wall box must be explicitly approved by the grid operator. A wall charging station with less than 12 kilowatts, on the other hand, only needs to be registered. However, a "yes" from the grid operator to the 22-kW wallbox is not certain. If he says "no," the only option is to purchase an 11-kW wall charging station. Regardless of whether it's a 22-kW or 11-kW wall box: You must hire a specialist company for the installation.

11-kW is enough for relaxed charging overnight

On the road, when every minute of charging counts, especially along highways and freeways, charging power plays an important role. That's why public fast-charging stations for electric vehicles are chasing record after record.

But at home, charging time plays a subordinate role. Your car is parked in your driveway or garage for several hours anyway. For example, if you get home at 7:00 p.m. and leave again at 7:00 a.m., your car has a full 12 hours to charge. It can also use this time to charge in a relaxed manner, for example at the tried-and-tested Heidelberg Wallbox Home Eco, the Heidelberg Wallbox Energy Control with load management or the new Amperfied Wallbox connect.home with app connection. It doesn't matter whether the car is charged in 6 or 12 hours.

Conclusion

There are 4 solid reasons for a wallbox with 11 instead of 22 kW:

  1. 11 kW has become the universal language for AC charging, i.e. charging with alternating current. Almost all modern electrified cars support 11 kW, whereas only a few support 22 kW.
  2. Charging at 11 kW is kinder to the battery, because slower is always better for a battery.
  3. A domestic charging station with a maximum charging power of 11 kW only needs to be registered with the network operator. Prior approval, as is required for 22 kW, is not necessary.
  4. At the wallbox at home, the car usually charges overnight. During this time, even the largest batteries at 11 kW are at least 80 or 90 % full.