Wattage is the overall measurement of power that flows through your charger. Therefore, higher wattage is faster charging. Some chargers or phones are listed with volts and amps. Wattage is the volts multiplied by the amps. Different devices can handle different amounts of wattage. Even though almost all devices can handle any amount of wattage, it may cause the device to overheat itself and ruin its battery. An example of a device is an iPhone. The iPhone can only charge at a maximum of a certain wattage. The excess wattage will become runoff heat which will cause the iPhone to overheat and cause the batteries health to permanently decrease.