Where is specified the max charge at which a macbook air can be charged ?

[chilean]

I see many alternative chargers 67 W etc. but it may be a waste if the mac book air doesn't support 67 W anyway.
Apple ships charger with their product, but do they ship the optimal power one ?

 

[Howard2k]

70W - 72W for the M3, it seems that the M4 is likely to be the same.

 

[raythompsontn]

The MacBook, Pro or Air, will only take as much wattage (current as the voltage is constant) as the device allows. A person could attach a 1,000 watt charger and it would not harm the device. The higher the wattage, the faster the charge, up to the device limit. I can easily charge my MBP overnight, from 20% to 100% using just a 35 watt charger. How long it takes I don't know, and don't care as long the charge is full by morning. I can do the same charge delta with a 100 watt charger in a couple of hours.

Whether Apple ships with the optimum charger is open to debate and that is largely influenced by the person's needs. Unless the need exists for rapid charging, then a lower wattage charger will work just fine. I prefer the smaller, thus less wattage, charger when traveling as it is less weight and bulk. Charging overnight with a 35 watt charger works just fine for my needs.