We demonstrate the hydrothermal synthesis of long copper nanowires based on a simple protocol. We show that the purification of the nanowires is very important and can be achieved easily by wet treatment with glacial acetic acid. Fabrication of random networks of purified copper nanowires leads to flexible transparent electrodes with excellent optoelectronic performances (e.g., 55 Ω/sq. at 94% transparency). The process is carried out at room temperature and no post-treatment is necessary. Hybrid materials with the conductive polymer PEDOT: PSS show similar properties (e.g., 46 Ω/sq. at 93% transparency), with improved mechanical properties. Both electrodes were integrated in capacitive touch sensors.