Analysis of electricity, water, and hot water consumption in NZEB apartments

¹ Haseko Corporation, Technology Promotion Division, 3-1-1 Tsurumaki, Tama-shi, Tokyo 206-0034, Japan
² Shibaura Institute of Technology, Graduate School of Engineering and Science, Department of Architecture, 3-7-5 Toyosu, Koto- ku, Tokyo 135-8548, Japan

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

This study examined electricity, water, and hot water consumption in an apartment building that has been retrofitted to meet Net Zero Building (NZEB) standards. The building, originally constructed in 1990, underwent insulation and equipment upgrades, and retrofitting was completed in September 2023. Measurement systems were installed in selected units to monitor consumption in both private and common areas under real living conditions. Data were collected from May 2024 to February 2025, during which the occupancy rate remained stable. The analysis revealed seasonal and time-based consumption trends. Electricity use increased in winter and decreased during intermediate seasons, with peak usage occurring between 18:00 and 22:00, especially at 20:00. Water consumption remained stable throughout the year and was unaffected by outdoor temperature. In contrast, hot water consumption increased in winter and decreased in summer, following a time-based peak pattern similar to that of electricity. This study successfully captured real-world utility usage patterns in a retrofitted NZEB apartment building. These findings provide valuable insights into electricity, water, and hot water demand behaviors, thus contributing to the development of more effective energy-saving strategies in residential buildings.