This paper proposes the conditional demand analysis (CDA) methodology, which is relevant in electric energy consumption by main household facilities and suggests important variables that can affect CDA values, accordingly. Although households, particularly apartments, are considered the main primary energy- and electricity-consuming housing type in Korea, efforts on reducing electricity consumption by households are limited. The usage of energy is mainly focused on primary energy. Considering that many attempts have been made to reduce residential energy consumption, disaggregating total electric energy consumption into specific end-use level such as heating, cooling, ventilating, hot-water supply and lighting, is a very useful method. In general, by obtaining information on the energy consumed by each piece of equipment, we can easily determine the total electric energy consumed.