Aesthetic appreciation affects the success of products in a number of areas, such as user satisfaction and usability. Hence, designers apply aesthetic principles to create more successful products. However, it is still unclear how such principles apply to the services and systems that products are often part of. In this paper, we explore how two aesthetic principles, which are known to influence product aesthetics, can be extended to product-service systems. These principles are Unity-in-Variety and Maximum-Effect-for-Minimum-Means. According to the former principle, aesthetic pleasure can be attained from perceiving as much variety as possible within a unified whole; according to the latter, it can be attained from perceiving efficiency. With the qualitative study here presented, we showed how the principles could also describe product-service systems in terms of their sensory properties, underlying mechanism and human interaction. We thereby offer a basis to further investigate and enhance the aesthetics of product-service systems.