7 kW, 11 kW or 22 kW: choosing AC charging power

The kilowatt figure on an AC charger is a ceiling, not a promise. What a vehicle actually draws depends on two things: the supply at the site, and the charger built into the car. Getting those two right matters more than picking the biggest number on the box.

What sets the real charging power

An AC charger passes mains power to the vehicle, and the vehicle’s on-board charger converts it to DC for the battery. The lower of the two limits wins: a 22 kW charging point cannot push 22 kW into a car whose on-board charger accepts 11 kW.

The supply side is arithmetic:

• 7.4 kW — 32 A on a single-phase 230 V supply.
• 11 kW — 16 A on a three-phase 400 V supply.
• 22 kW — 32 A on a three-phase 400 V supply.

When each one fits

7.4 kW is the practical ceiling for most homes with a single-phase supply, and for many overnight patterns it is enough: roughly 59 kWh over eight hours, more than a typical daily commute needs.

11 kW is the common European three-phase default. It nearly doubles overnight energy (about 88 kWh over eight hours) without demanding the full 32 A per phase, which leaves headroom for the rest of the building.

22 kW is for sites where cars turn over quickly or several vehicles share a short window — workplaces, shops, small fleets. It needs a three-phase supply with capacity to spare, and a car that accepts 22 kW on AC; many models stop at 11 kW.

The supply is shared, not dedicated

On a site with other loads, the charger is rarely the only thing drawing power. Dynamic load balancing measures what the building is using and reduces charging current to stay within the supply. On our DLB charger the minimum charging current is 6 A; below that it stops rather than disturb the rest of the installation. That floor, not the headline kW, is often the number a project is designed around.

Wall-mounted, pole-mounted or portable

The power decision does not fix the form factor. The same 7.4–22 kW range is available as wall-mounted units, as chargers embedded into lamp posts, and as portable units with interchangeable plugs. For shared parking and courtyards, pole-mounted units avoid new posts and clutter; for a single driveway, a wall box is usually simpler.

Questions that decide it

• Is the supply single-phase or three-phase, and what current is available?
• What does the vehicle’s on-board charger accept?
• How long is a car normally parked, and how many cars share the point?
• Is there other load on the supply that the charger must work around?

Answer those four and the kW figure usually chooses itself. Standard models are CE and RoHS compliant. Customised builds require additional CE and RoHS certification, which we confirm at quotation.

Next step: see the European AC charger, the 11 kW portable charger and the 22 kW portable charger, or tell us the supply and the vehicles and we will recommend a configuration.

Shenzhen Holeetech Co., Ltd. manufactures AC chargers from 3.7 kW to 22 kW in-house.