Among many retrofit options, lighting retrofit is one of the popular choices. This paper reports application of key performance indicators (KPIs) on assessing lighting retrofit performance in commercial buildings in Hong Kong. The importance level of KPIs including energy saving (%), payback period (year), investment cost ($) and target work plane illuminance (lux) were investigated. The projects involved lighting retrofits such as the replacement of energy-efficient lamps (e.g. LED). The scale of the lighting retrofit projects ranged from HK$0.1M to HK$3M, and the project periods were between 2 months and 3 years. Results showed that the average relative importance level (w) of target lighting illuminance level was 8%. It was also vital to consider the environmental and economic factors such as energy saving (w: 32%), payback period (w: 36%) and investment cost (w: 24%). The performance rating for target lighting illuminance was highest (average: 5 out of 5), followed by energy saving and investment cost (average: 4 out of 5), while payback period was rated the lowest (average: 3 out of 5). To further enhance energy efficiency in retrofit projects, more case studies can be conducted with the application of Artificial Intelligence technologies and examine its actual impact on energy saving.