Abstract Thermodynamic equations for the performance evaluation of the monomethylamine–water vapour absorption refrigeration system have been obtained, analysed and reported in this paper. These equations have been derived from experimental data with a good agreement with the expected values and have been expressed in polynomial form. These equations were utilized on the energy and mass balances for obtaining the coefficient of performance (COP) with this pair and compared with the ammonia–water absorption system. It has been observed that this refrigerant–absorbent pair has a greater coefficient of performance at low generation temperatures and moderate condenser, absorber and evaporator temperatures.