Respective energy consumption data is collected via respective agents running on respective host servers. The respective energy consumption data represents energy consumed by the respective host servers over a time period. The respective agents communicate with hardware on each of the respective host servers using a unified application programming interface (API). Respective energy costs are determined over the time period for the respective host servers based on the respective energy consumption data. A subset of the respective host servers that are being underutilized is identified based on the respective energy consumption data and the respective energy costs. An action to take with respect to the subset of the respective host servers that are being underutilized is determined to reduce the energy costs.