The study included an investigation to analyze the Absorption Heat Pump (AHP) and Absorption Heat Transformers (AHT) using ammonia-water and water-lithium bromide solutions. A fundamental AHP and AHT systems are described and the operating sequence is explained. Since the AHT systems widely use ammonia-water solution with ammonia as the refrigerant and water-lithium bromide solution with water as the refrigerant, the comparison of the two is presented in respect of the coefficient of performance (COP), the flow ratio (FR) and the maximum system pressure. It is concluded that the AHT system using water-lithium bromide solution provided better performance than the system using ammonia-water solution. (C) 2001 Elsevier Science Ltd.