Energy- and materials-efficient designs are highly valued in the context of sustainable product design, but realizing products with significant changes in efficiency is a difficult task. One means to address this challenge is to use biological analogies during ideation. The use of biological analogies in the design process has been shown to greatly increase the novelty of concepts generated, and many authors in the bioinspired design (BID) community contend that efficiency-related benefits may be conferred as well. However, there is disagreement in the field as to when, how, and why efficiency-related benefits might arise in BIDs. This work explores these issues in-depth. A review of BID literature and an empirical study of BIDs lead to a better understanding of the types of efficiency advantages conferred by BID and set the stage for the development of tools and methods to systematically generate more energy- and materials-efficient design concepts using biological analogies.