This study analyzes adoption trends of high-efficiency residential water heaters in Japan before and after the enforcement of the Building Energy Efficiency Act. Using shipment data by region from 2011 to 2024, changes in the adoption structure of electric heat pump, gas, and oil high-efficiency water heaters were examined. The results indicate a structural transition around 2015, with electric HP water heaters showing stable growth across regions, while gas water heaters reached market maturity and oil water heaters declined. Regional differences, particularly in cold climates, were also identified, highlighting the influence of housing and energy conditions on technology adoption.
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HASHIMOTO et al. (2026) studied this question.
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