Bluetooth class 3 is 1 mW peak power, class 2 is 2.5 mW peak power. Those are the most relevant for a headset. For a cell phone, the peak power for 2G is 2W, w

Bluetooth class 3 is 1 mW peak power, class 2 is 2.5 mW peak power. Those are the most relevant for a headset. For a cell phone, the peak power for 2G is 2W, while for 4G/LTE it's 200 mW. Those are peak transmit power. In practice the actual power will be lower for BT. For cellular it depends very much on the frequency band used. For low band the phone will mostly be far from the peak. For high bands the device will mostly be at peak power or close most of the time.