Abstract A thermodynamic analysis was carried out to study the performance of single-stage, two-stage and double-absorption heat transformers operating with the water/Carrol mixture, where Carrol is a mixture of lithium bromide and ethylene glycol [(CH 2 OH) 2 ] in the ratio 1:4.5 by weight. A mathematical model to predict the theoretical performance of single-stage and advanced heat transformers operating with the water/Carrol mixture is also described. Coefficients of performance and gross temperature lifts are compared for the different heat transformers and plotted against the main temperatures of the system. A two-stage heat transformer consists of two single-stage heat transformers which can be coupled in three different ways. A double-absorption heat transformer is a single-stage heat transformer to which a dual-purpose absorber/evaporator unit has been added.