The peak is solved by sharing, not by contracting
In the seven-to-nine band there may be more cars connected than there is power to charge them all fully. The right answer is not to contract more power, because it would be paid for all year to be used two hours: it is to share the available power between the connected cars.
In a stay of an hour and a half, a member recovers enough for their daily use even at reduced power. The perception of service holds up and the fixed cost does not shoot up.