Currently the most popular is the 20 W charger. Let me tell you how you can make the right choice without having to argue about whether or not you should use 20 watts on your phone. You need to have a rough understanding of Watt, Ampere, and Volt to see how many watts your phone battery has and how many Watt Chargers you would use. Watt is Power. The amount of power is the same as the number of watts. Another type can be considered as a complete wattage.