In Product-Service Systems development, understanding of the customers' use of goods seems vital, since the product per se is not sold but rather the performance it brings to the customers' processes in terms of added value. This changed business scenario insists on an integration of a service and a product perspectives in early design phases. However, the approaches to understand customers diverge. In this paper, a need matrix, from the economic theory of needs, and a requirement matrix, from the TRIZ methodology, are used to elaborate on integration aspects to understand customer statements. The comparison of these matrixes made the distinct logics apparent, and gave an indication for the necessity of another type of specification for PSS products. Also, the knowledge base for PSS methodologies has to be extended to encompass a part that visualizes non measurable aspects such as needs.