Power data alone cannot identify sources of energy inefficiency. However, correlating power data with utilization statistics can reveal where power is used well and where it is wasted. We describe a sensing infrastructure, PowerNet, that monitors power and utilization in a building environment. The deployment includes both wired and wireless sensors and covers offices, networking closets, and server racks. We present PowerNet's architecture, then generate initial insights from each monitored environment. Analyzing PowerNet data traces identifies contexts where electricity consumption can be reduced without cost, and others which call for rethinking system designs altogether.