Energy Monitoring System for Existing Buildings in Indonesia Sentagi Sesotya Utami, Faridah, Na’im A. Azizi, Erlin Kencanawati, M. Akbar Tanjung and Balza Achmad E3S Web Conf., 42 (2018) 01003 Published online: 29 June 2018 DOI: 10.1051/e3sconf/20184201003