<p>Optimal design of refrigerators is crucial in terms of reducing energy consumption due to their extensive use. Determining an optimal design experimentally is difficult, time-consuming, and costly trial and error. In contrast, simulation-based design processes are effective and reduce costs. This study presents a novel quasi-steady simulation model for side-by-side household refrigerators that integrates the effects of frosting and defrosting on the evaporator, advancing current methodologies in refrigeration system modeling. The research combines steady-state modeling of key cycle components with transient modeling of compartment conditions. The model was validated using experimental data collected under controlled hot room environments at ambient temperatures of 32 °C and 43 °C, demonstrating a maximum error of 10 % in pressure predictions, 2 °C in temperature predictions at different points of the cycle, and 10 % in power consumption prediction. The proposed model also estimated the temperature increase of the evaporator surface during frost formation with a maximum error of 5 °C. In addition, refrigerant mass flow rate, frost thickness, and mass accumulation were accurately calculated by the model, providing a robust framework for energy efficiency evaluations.</p>