Unless you eventually buy a vehicle with a larger charging circuit (BTW, the charging circuit is IN the car - the box is just a fancy switch to provide it with the power it needs), you're then paying for heavier wire, bigger circuit breaker, and a more expensive unit. Next gen vehicles will likely have bigger batteries, and MIGHT have a larger ability to charge them, but they may just limit the expense of the on-board charging circuit and just require you to wait a little longer. IT won't hurt anything except your pocketbook to install a larger one than you need today, and could save you some money down the road if you buy one that COULD use more, but it would still work, regardless. The EVSE sends out a signal that tells the car how much it can provide, and if the car is working properly, will never ask for more than can safely be supplied. This is why the unit that comes with the car can work...in the USA, that one only provides a maximum of 12A, and it works, but slowly, and doesn't overload the receptacle it gets plugged into because the car never asks for more than what the unit says it can provide.