Abstract: Energy User (EU) can benefit from implementing Energy Performance Contract (EPC) projects. However, it is unclear how an EU can select an Energy Service Company (ESCO) efficiently from multiple candidates so as to maximize its interests. This arouses two particular questions:one is which method can be used by the EU to select asuitable ESCO, and the other is which indicators can be adopted to achieve effective outcomes toward ESCO selection. In practice the main concern of the EU is how to determine an optimal ESCOdepending on insufficient ESCO information. This paper aims to investigate the optimal ESCO selection problem from the perspective of the EU by using the weighted multi-objective gray target decision model. The weighted multi-objective gray target decision model is first introduced, followed by determining main decision-making objectives of ESCO selection based on a two-round expert consultation. Then according to different types of the decision-making objectives (i.e. benefit-based, cost-based, moderate),the objective effect sample matrix are formulated and the objective effects' threshold values are set. Finally, by calculating the uniform effect measurement matrix, the dimension of the three ESCOs' objective effect sample matrix is dispelled. The ultimate optimum of ESCO is identified by judging the three ESCOs' synthetic effect measurement values. The study reveals that in the process of determining an optimum ESCO, special attention should be paid on aspects including ‘the qualification of ESCO’, ‘the reputation of ESCO’, ‘the quality of energy-saving equipment’, ‘energy-saving retrofit period’, ‘energy-saving benefit sharing period’, ‘energy-saving design’, ‘participants’ energy-saving benefit sharing proportion, ‘the damage extent to the original building components’, ‘energy-saving during the contract period’, ‘feasibility to spot energy-saving volume’ and ‘pre-payment’. It is also proved that applying the weighted multi-objective gray target decision model to optimum ESCO selection could largely help the EU to address the problem effectively even the EU faces a dilemma of scarce data and information about the ESCO.

Key words: energy performance contract, energy service company, gray system theory, weighted multi-objective gray target decision model