Assessing Green Information Technology (IT) maturity in organizations is a relevant process to measure the progress of sustainable IT initiatives and to support new actions to improve them. Knowledge about the organizational maturity level in Green IT and comparing this level with those of other companies are necessary for self-assessment to strengthen organizations' general sustainability strategy. The main objective of this paper is to communicate a Green IT maturity assessment model with its class structure. This model can also provide benchmarking regarding organizations' maturity since its fundamental premise is a pairwise comparison between companies to obtain their classification. Based on a literature search to identify the existing maturity models, the CMMI model was selected since it is the most recurrent in the literature on managing organizational Green IT actions. The classification process using CMMI maturity levels as classes is based on the ELECTRE IV multicriteria decision support method, which was developed to work specifically with classification problems. The results include the companies' allocation into the most appropriate classes, considering well-defined criteria set with their weights, the class boundaries according to numerical parameters such as lower and upper limits for each of them, and data collected with companies under consideration for the assessment.