Compactness and portability of MEMS sensors and actuators with dedicated power sources are governed not only by the size of the system components but also by the size and durability of the power source itself. This work is part of a project on the characterization and modeling of heat transfer of an on-chip assembly of RTDs (resistance temperature detectors), microthermocouples and thin films of different materials. In this paper, we investigate the effects of conductive and convective heat transfer on the response of an RTD. Especially, the effects of a range of pressures from atmospheric to near-vacuum conditions at different applied voltages on the electrical energy consumption of an on-chip RTD are investigated. The transient temperature - time response as well as the power consumption of the RTD under the aforementioned conditions are also reported. Conductive effects are far more important than any other heat transfer mechanism; these effects are quantified.