Wattage of charger Apple Watch three series

You can charge an iPhone, iPad or iPod Touch (or Apple Watch) with any quality USB-A or USB-C power source and matching cable. Essentially any Apple power source and cable that fit into the connectors at either end are compatible and safe to use. There will be performance differences, with USB-C faster than USB-A to charge, but they will all work (except that a USB-A “cube” doesn’t have sufficient power to charge an iPad). For an iPhone 12 or later you can fast charge using a 20 watt or higher power USB-C that meets the PD spec. The Apple 20 watt and higher is PD compatible, but not all 3rd party power sources are yet.

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• The "charger" for an iOS device is built into the device. It is not the thingy that plugs into the wall, and it is not the cable that connects the thingy that plugs into the wall to the phone. They are just a source of current and a way to get it to the phone, respectively.

and see:

When to charge your iPhone or iPad - Apple Community