Abstract Vapour absorption heat transformers are thermodynamic cycles which are capable of upgrading the temperature of waste heat energy using only negligible quantities of electrical energy. Although marked as a future technology by the IEA (International Energy Agency), as being important for energy utilization in the 21st century, industrial applications of heat transformers are still very limited. This paper presents a comprehensive review of heat transformer research over the past two decades. Emphasis is placed upon optimisation studies, alternate cycle configurations, working fluids comparisons and industrial application case studies.