The presence of immature concepts makes difficult decision making at upstream phase of a development project. Rework tasks in collaborative development projects dealing with immature design concepts are very frequent and are responsible of cost overruns and schedule delays. In addition, decisions taken during conceptual design stage have the most important influence on product life cycle cost. In this context, a useful practice is to develop two or more concepts in parallel and delay decision making. Even so, a first screening of concepts is usually needed because of the substantial resources and time required in development phase. In this paper, an approach of concepts screening is proposed at conceptual design phase on the basis of two metrics. The first assesses ability of concepts to meet requirements with integration of maturity. Fuzzy logic tools are used to capture and propagate imprecision in embodiment design choices and behavior models. The second metric aims to assess expected performance of novel concepts compared with an existent product. It uses generalized ordered weighted averaging (GOWA) operator. A parametric aggregation function is also proposed as a support when using the two metrics. The proposed approach was applied to the development of a solar collector.