Japan has shut down more than 70% of its nuclear power plants since the March 2011 Tohoku earthquake and the ensuing accident at the Fukushima Daiichi nuclear power plant. The country has been challenged with power shortages in the short-term and faces complex energy security decisions in the long-term. Japan has a long history of implementing energy conservation policies, such as the Top Runner Program, which covers 23 products including appliances and industrial equipment. However, Japan's efficiency policy for polyphase electric motors is considered below international standards. Polyphase electric motors accounted for about 55% of the nation's total power consumption in 2008. The aim of this study is to estimate potential energy savings and reduction in CO2 emissions (2014–2043) by examining scenarios involving adopting two different polyphase motor efficiency standards and comparing them to a base case and concludes by suggesting pathways for further policy development using the results obtained. The study finds that if level IE2 of the international efficiency standard IEC 60034-30 were implemented, it would save 8.3 TWh (or 0.03 quads) per year, which is equivalent to about 0.8% of Japan's total electric power consumption in 2010. If level IE3 of the IEC 60034-30 were implemented instead, it would save about 13.3 TWh (or 0.05 quads) per year. The corresponding cumulative energy savings and reduction in CO2 emissions for the IE2 scenario would be 249 TWh (or 0.85 quads) and 93 Mt. The corresponding cumulative energy savings and reduction in CO2 emissions for the IE3 scenario would be 398 TWh (or 1.36 quads) and 149 Mt.