The growing popularity of mobile video streaming necessitates a clear understanding of its power consumption on mobile devices. Different from previous work, we focus our attention on the impacts of adverse network conditions, and study how power consumption of mobile video streaming apps changes under different scenarios. To this purpose, we conduct a measurement study in this paper on power consumption of mobile video streaming apps under various network conditions. We build a small testbed to investigate the impacts of packet loss rate, propagation delay and available bandwidth. Our measurement results show that power consumption increases significantly when network conditions become worse. The power consumption of wireless data transmission is inversely proportional to the available bandwidth. Frequent packet loss and large propagation delay greatly decrease the TCP throughput and prolong the WNIC's busy period, which in turn consumes more battery energy. Finally, we discuss a few implications of our results on power optimization of mobile video streaming apps.