Recent studies indicate that the Internet-related energy consumption represents a significant, and increasing, part of the overall energy consumption of our society. The largest contribution to this consumption is due to Internet edge devices. Typically, users leave their PCs continuously on for satisfying the connectivity requirements of file sharing p2p applications, like BitTorrent. In this paper we propose a novel proxy-based BitTorrent architecture. BitTorrent users can delegate the download operations to the proxy and then power off, while the proxy downloads the requested files. We implemented our solution and validated it in a realistic testbed. Experimental results show that, with respect to a legacy approach, our solution is very effective in reducing the energy consumption (up to 95%) without introducing any QoS degradation.