Energy is a key feature that must be explicitly managed for long-term autonomous robotic missions. Many research studies have addressed the energy issue, developed energy-aware motion control or integrated energy in mission objectives. However, few studies have comprehensively assessed the impact of software and hardware choices on power consumption of robots. Based on experimental analysis and according to the selected control scheme and hardware configuration, this paper proposes energy consumption models for the Pioneer 3DX. The proposed models highlight the existence of an optimal velocity that minimizes motion energy. These models are experimentally evaluated and discussed.