This study presents a comparative evaluation of two detached houses constructed in different climatic regions of Japan — cold and warm region — to investigate the relationship between energy consumption, equipment performance, and indoor thermal environment under actual occupancy. Both houses feature high insulation performance, solar power generation, and heat pump systems for space heating, cooling, and domestic hot water. Long-term field monitoring exceeding ten years has been conducted to clarify regional differences and occupant influences. In the warm region, the measured energy use was compared with design predictions, followed by analyses of year-to-year variations in end-use energy. Subsequent retrofitting of the hot-water storage insulation achieved approximately 17% reduction in winter DHW energy, and the building-integrated photovoltaic system exhibited only 0.3% annual degradation over eight years. In the cold region, after occupant changes, the household showed lower heating demand due to behavioral adaptation and the introduction of auxiliary heating devices. The measured indoor temperatures were generally maintained between 21°C and 23°C with relatively low electricity use. These results demonstrate that even under different climatic conditions, high-performance detached houses can achieve low energy consumption and comfortable indoor environments when appropriate system design, operation control, and occupant behavior are integrated. The findings contribute to the development of regionally optimized design and operation strategies for energy-efficient housing in Japan.