Traditionally functionality and aesthetics are two main aspects that product designers use to design innovate a product. With the increasing emphasis on environmental sustainability, in recent years sustainability has gradually become another important aspect that product designers also consider in the product design innovation process. This study focuses on scrutinizing the trade-offs of functionality, aesthetics and sustainability from the consumer perspective. Results of consumer experiments demonstrate that these trade-offs are more complex than originally thought. The self-identity theory has been used to help explain these trade-offs.