With the increases in residents’ household energy consumption and carbon emissions, to conserve regional energy and reduce emissions, studying the factors affecting residents’ willingness to purchase energy-efficient appliances and their mechanisms of action is necessary. In this research, based on the theory of extended planned behavior and combined with environmental concern variables and environmental knowledge variables, a model of the factors influencing residents’ willingness to purchase energy-efficient appliances was constructed and an empirical study of urban residents in Shanxi Province, China was conducted. The research indicates that environmental concern, environmental knowledge, attitude, and perceived behavioral control are significantly positively correlated with residents’ willingness to purchase energy-efficient appliances. The influence of subjective norms on the willingness of residents to purchase energy-efficient appliances is not significant; environmental concern and environmental knowledge have a positive impact on attitudes and indirectly affect residents’ willingness to purchase energy-efficient appliances. This study focuses on improvement and research from the perspectives of theoretical expansion, indirect impact test, and analysis of typical underdeveloped energy-rich regions. This study provides corresponding policy suggestions from the perspectives of education and guidance, sales and marketing, and independent improvement for the government, sellers, and residents, to improve the residents’ willingness to purchase energy-efficient appliances.