Nowadays, it is estimated that half the connected devices are related to the Internet of Things (IoT). The IoT paradigm contributes to the increase of the Information Technology energy demand. The energy demand is due on one side to the huge number of IoT devices, and on the other side to the plethora of IoT end user applications consuming data produced by those devices. However, taking into account energy consumption in the development of such applications, consuming data produced by IoT devices is still challenging. There is a lack of knowledge on what are the best practises to develop green IoT applications. The work presented in this paper aims to raise the awareness of application designers concerning the impact of the choice of IoT protocols and interaction patterns on the energy consumption of the applications. For this purpose, we have experimentally analysed the energy consumption of HTTP and MQTT, which are two of the most popular, mature and stable protocols for IoT consumer applications. For the HTTP protocol, we have studied both the publish-subscribe and the request-reply interaction patterns. For MQTT, we have studied the publish-subscribe interaction pattern with the three available Quality of Services. We also examine the impact of message payload on energy consumption. The results show that the publish/subscribe interaction pattern has lower energy consumption (around 92% less) than the synchronous interaction pattern and HTTP consumes 20% more energy than the MQTT protocol for the publish/subscribe interaction pattern. Finally, we show that the payload has a low impact on energy consumption, having a 9% overhead on payloads ranging from 24 to 3120 bytes.