The growing recognition of the Sustainable Development Goals (SDGs) has been integrated globally into product design and business activities. Life cycle assessment (LCA) is considered a useful tool for designers to apply in the early stages of product design to mitigate the environmental impact. The study aims to identify the challenges of applying simplified LCA tools to improve the eco-efficiency of products and achieve a higher level of sustainable innovation. The study was conducted in a sustainable design course at Chulalongkorn University, Bangkok, for four consecutive years. All challenges and opportunities by using ECO-it, Eco-indicators, and the Materials, Energy use, and Toxic emissions (MET) matrix to assess the environmental impact in each phase of 11 home appliances are presented and discussed. Results show the positive potential of applying the tools to achieve function innovation in design for sustainable innovation. The needs for guided instruction, the availability of the database, the complexity of a study product, and the overlooking of social dimensions are four major challenges in applying the tools in the early stages of product redesign. Further study in testing the tools and developing a database in collaboration with industries should be conducted to compare and validate the results.