Semarang city in Central Java has natural lighting from sunlight, throughout the year and can be optimized when integrated with artificial lighting. It will be reduce electrical consumption. Research in lecturer’s workspace in Gedung Pusat UPGRIS performs a simulation analysis of natural and artificial lighting and their integration using the Dialux EVO version 9.0. The simulation results of the existing condition of natural lighting is 164 Lux (09.00 AM) and 225 Lux (01.00 PM), while the existing simulation results provide 201 Lux with a power consumption of 1.69 Watt/m2. The results of the integration natural and artificial lighting produce 265 Lux (09.00 AM) and 256 Lux (01.00 PM) with the same electrical consumption of 0.84 Watt / m2. This value shows that the existing simulations of natural, artificial and integrated of them are still less than the SNI 16-7062-2004 standard is 350 Lux. The first retrofitting by changing the type and number of lamps resulted in 393 Lux higher from SNI standard 350 Lux. The simulation produced 556 Lux at 09:00AM and 648 Lux at 01:00PM, veryhigher than SNI standart 350 Lux. Through this retrofitting approach, artificial lighting at night shows minimum standard because no light. The second retrofitting effort is to turn off the lights automatically Lux sensor in the workspace area near the windows the natural lighting is strong enough, the results show that the illumination strength of 402 Lux at 09:00AM and 494 Lux at 01:00PM with low electrical consumption during the day becomes 2.92 Watt/m2.