The energy and environmental merits of three types of internal-combustion-engine primed trigeneration (ICEPT) systems were investigated when compared with a conventional chilled water system powered by the grid electricity for use in a high-rise office building in Hong Kong. With the employment of the ICE PT systems, the year-round total electricity demand from the building was reduced by at most 10.4% for the natural-gas-fueled one. However, the saving in the total primary energy consumption (PEC) only ranged from 1.7% to 6.8% with the diesel-oil-fueled system being the best although for all the three types of ICEPT systems more than 70% of the energy from the fuel had been utilized. The huge difference in the coefficient of performance (COP) between the absorption chiller and the vapor-compression chiller was the main cause which impaired the benefit of recovering the waste heat to provide space cooling. The total carbon dioxide emission (CDE) varied widely with the types of fuels adopted with a maximum of 26.7% for the natural-gas-fueled system which was due to the lower carbon dioxide emission index of natural gas as compared to other fuel types. The overall ranking of the ICEPT systems depended on the weighing between energy and environmental merits. (C) 2014 Elsevier Ltd. All rights reserved.