Abstract Combined heat and power (CHP) systems involve the simultaneous release of electrical (or mechanical) power and heat in the form of low-pressure steam or hot water. The assessment of the economic viabilities of mini-CHP packages and the predictions of their thermodynamic performances usually involve tedious and prolonged numerical exercises. Thus an existing software package has been modified and extended to handle this type of problem comprehensively, yet in a simple, routine and rapid manner. The pay-back period is estimated to be less than three years for the required mini-CHP package installation to satisfy the power and heating demands of each simulated two-storey hotel.