Total Cost of Ownership (TCO) is a method to describe all costs of a certain infracstructure. In an early approach the concept by Gartner Group in the late 80ies estimated the costs of a working place (PC) of an ICT environment.
Later on some consulting companies extended this concept by refining the methods (such as RCO or TEI). Anyway the term TCO is still present today but in a wider sense of course, though there is no common standard of how to get comparable TCO-figures unfortunately.
This is where the TCO-Tool may help: A well defined Cost-Model linked to a
transparently modelled system (Base-Information or TCO-Objects)
shall be the base for standardized and interpretable TCO-comparisons.