The LoRa radio transmission is a popular low power WAN technology due to the use of unlicensed spectrum, low cost and long-range. LoRa devices use different Spreading Factors, which are dynamically selected by an Adaptive Data Rate (ADR) algorithm, based on signal-to-noise ratio (SNR) measurements. We discuss the influence of ADR parameters on the network performance. We use extensive simulations to estimate the probability of message delivery and energy consumption for different configurations of ADR parameters. The analysis has been performed using OMNeT++ Discrete Event Simulator together with FLoRa framework for two types of network topologies: random uniform and based on a sample city-wide LoRa deployment. The results show that there is a significant trade-off between the energy utilization and message delivery ratio probability and that the default configuration of ADR leads to over-optimistic decrease of SF and TX power, as a consequence leading to packet loss ratio >50 %.