An important characteristic of video transmission over wireless channels is that the channel is error-prone and the compressed video data is highly sensitive to errors. The transmission errors will cause decoding failure which will distort the reconstructed pictures. One of the challenging issues in wireless video communication system design is to minimize the overall energy consumption and maximize the operational lifetime of the devices. In this work, we focus on the energy consumption in wireless video transmission. Based on a transmission distortion model, we develop a rate-distortion optimized transmission power adaptation scheme for video streaming over wireless channels. Our experimental results demonstrate that this scheme is able to significantly improve the video quality under the transmission power constraints.