The maximum amount of useful thermodynamic work that can be extracted from a system in a given surrounding. This can be mechanical work such as running a pumping or lighting a bulb with electrical energy. For example, there is more exergy in an ice cube in a room at ambient temperature than a cup of water in the same room. It applies to kinetic, potential, chemical, nuclear, magnetic, and electric energy. Exergoeconomics is the study that combines exergy analysis with process economic evaluation to identify the cost of operating a system in terms of materials in, products out, and the cost of exergy destruction. It is used for the analysis of many processes in terms of the amount of work that can be lost or needs to be applied.