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Lighting is considered as one of the most important issues in reducing energy consumption of a building. It is estimated that electrical lighting consumes 25-40% of the total electrical energy in a typical commercial building in the United States. Over the last three decades, there has been a growing concern about reducing energy consumption associated with artificial lightings. Daylighting could be considered as a cost-effective alternative to artificial lighting which not only reduces the demands for electrical energy, but also provides occupants with a pleasant, attractive, and a healthy indoor environment. Through installing sensors and controllers, daylighting is able to reduce and even eliminates the use of artificial lighting needed to deliver sufficient illuminance levels in an office. Present study is a simulation based research that investigates the impacts of various types of daylighting controllers on enhancing total and lighting electrical energy consumption of office buildings located in hot climates. Effects of Dimming (5%, 10%, and 20% light), On/Off, and Stepped control systems are evaluated in this study. E-Quest is used as the energy simulation tool to calculate and compare electrical and lighting energy consumption. In order to assess the effects of daylight control systems in humid and arid hot climates, Miami, Phoenix, and Houston, located in ASHRAE 90.1 climate zones of 1A, 2B, and 2A respectively, have been chosen as three locations for the prototype building. The prototype building is a four-story open office building measuring 18 m wide x 36 m long x 15 m high oriented along east-west axis. The window to wall ratio of 20, 40, 60 and 90% in all directions are assessed. Windows consist of horizontal shading in all facades as well as blinds in those of East and West. Results of this study demonstrate that in all studied cities installing daylighting controllers in office buildings significantly reduces electrical energy consumption of the building particularly that of lighting. (C) 2017 Elsevier B.V. All rights reserved.