The 7Kw EV Charger are designed to be put on a single phase supply which are mostly found in domestic properties and charge your car on average 30 miles her hour.
Whereas a 22Kw EV Charger can only be supplied on a 3 phase supply which are mostly found in commercial places like hotels, offices etc.
22Kw chargers give you up to 90 miles per hour. Three times the amount of a single phase charger.