The residential building sector utilizes over 37% of the total electricity consumption in Qatar. This paper summarizes the results of the first comprehensive field testing and energy analysis of residential buildings in Qatar. Specifically, the study is based on detailed energy audits for over 10 residential buildings in Doha to assess their characteristics and their energy efficiency level. In addition to walk through audits, detailed testing of building systems, as well as long-term monitoring of whole-building energy consumption are carried out and presented. Moreover, the paper provides the results of a questionnaire administrated to the occupants of residential buildings to determine their occupancy schedules and pinpoint their behavior patterns in utilizing various energy systems. The results of the energy audits, occupant surveys, and energy monitoring are combined to develop detailed and calibrated energy models for all the residential buildings. The calibrated energy building models are then utilized to identify through detailed simulation analysis, optimized energy efficiency improvements that can be considered in the future design of residential buildings in Qatar. Specifically, the results of an optimization based net-zero energy retrofit of residential buildings in Qatar are discussed.