LoRa is a technology for long range wireless communications that allows the development of new applications in domains such as smart agriculture, smart city or smart industry. Many in-field deployments and measurement campaigns have been performed in recent years, showing the sensibility of such communication to fading channels. In this paper, the LoRa transmission reliability is evaluated in simulations for different fading channels. Moreover, as the energy consumption also depends on the configurations, a trade-off between energy consumption and reliability needs to be considered when selecting a LoRa configuration. To this aim, experimental energy measurements are performed on a Semtech device, showing that energy difference between various configurations can reach up to two orders of magnitude. Results highlight that LoRa configuration impacts the energy/reliability trade-off and the best one strongly depends of the type of channel.