Performance map-based modeling has been commonly employed for the rapid prediction of air conditioning and heat pump steady state performance. This approach requires that performance characteristics of the compressor and heat exchangers can be expressed in the form of simple algebraic functions. The growth of microprocessor based control, particularly in residential systems, has led to more frequent off-design operation. This study explores the ability of the map-based modeling approach to predict off-design operating performance of a single air-source heat pump operating in the cooling mode. Off-design conditions were simulated by varying the evaporator air flow rate over a wide range. Performance predictions are compared with the predictions of a more rigorous heat pump simulation program which utilizes heat transfer correlations for the heat exchangers rather than performance maps. A PC math package was used to generate results for the map-based model, while a Fortran compiler was used to generate results for the more rigorous model. The benefits of the map-based approach in predicting system performance are presented and discussed.