Small- and medium-sized enterprises (SMEs) collectively account for >13% of total global energy demand but have not receive sufficient scholarly attention because of the lack of an integrated framework to investigate the decision-making process of energy-efficiency measures (EEMs) and its crucial influencing drivers. To improve the energy-saving capabilities of SMEs, we developed a framework to integrate notable contextual factors and a core decision-making model from decision essence and characteristics and conducted an empirical study in Taiwan. The integrated framework postulated that energy-saving credo affects the formation of an energy-saving routine, and the routines, in turn, determine the adoption of energy-saving behaviors. Energy-saving knowledge, participation level in energy-saving initiatives, energy-saving barriers, and energy-saving incentives are moderating factors for energy-saving behaviors. In our empirical study, 2001 valid questionnaires were collected from domestic SMEs, the response rate was 80.04%, and a majority of the hypotheses derived from the framework were validated using statistical analysis. Our research provides at least three implications. First, the research proposed the credo–routine–behavior model, a core decision-making processes of SMEs, supported by empirical data. This empirically supported model implies that altering the credo of a company can change its behavior. Second, energy-saving knowledge, incentives, barriers, and initiatives are the contextual factors, and merely manipulating these factors cannot induce expected energy-saving behaviors in SMEs. Third, because SMEs may participate in many energy-saving programs simultaneously, governments should develop a package of energy-saving policies for SMEs that corresponds to their credos and knowledge, not only to their barriers.