An energy management system (EnMS) is a framework for energy consumers, including industrial, commercial and public sector organizations, to manage their energy use. It helps companies identify opportunities to adopt and improve energy-saving technologies, including those that do not necessarily require high capital investment. In most cases, the successful implementation of an EnMS requires specialized expertise and staff training. 

According to the International Organization for Standardization (ISO), an energy management system involves developing and implementing an energy policy, setting achievable targets for energy use, and designing action plans to reach them and measure progress. This might include implementing new energy-efficient technologies, reducing energy waste or improving current processes to cut energy costs.