An increasing number of devices are connecting to the internet, the so-called Internet of Things. Many of these devices use Bluetooth, which is a global standard for this purpose. Since they are often portable and battery-powered, energy efficiency has become an important factor. Different use cases have different characteristics in their network traffic, including the size of IP packets. This study has investigated how the size of IP packets affects energy consumption when devices using Bluetooth Classic and Bluetooth Low Energy communicate with IPv6. A testbed consisting of two Raspberry Pi 3 B+ devices was configured with BNEP for Classic and 6LoWPAN for BLE, after which data traffic with different packet sizes was sent, and the energy consumption was measured. The study shows that Classic is more energy efficient at a payload size of 64 bytes, however BLE was more energy efficient at payload sizes of 20, 256 and 1280 bytes.