<p>The environment control system (ECS) of an aircraft is essential for regulating the temperature and pressure and providing the ventilation for the cabin and avionics with respect to altitude and Mach number based on an air-cycle-based bleed or bleed-less system. However, various studies have been conducted on the thermodynamic analysis of the ECS, comparing bleed and bleed-less configurations for the high-pressure water-separation-based ECS. A comparative thermodynamic performance analysis of bleed and bleed-less membrane-based dehumidifier (MAD) ECS has not been explored in the existing open literature. To address this research gap, a steady-state thermodynamic model was developed to estimate the temperature and pressure profiles for both configurations of the MAD ECS at altitudes of 0–11&#xa0;km and Mach numbers of 0–0.85 by utilizing MATLAB. The credibility of the MATLAB code is validated against the existing literature on the bleed MAD ECS by comparing the temperature profiles of the main airflow path at critical points. The performance of both systems is evaluated in terms of the coefficient of performance (COP) parameter, and the effect of heat exchanger effectiveness and compression pressure ratio, altitude, and Mach number on COP is also carefully analysed in the study. The study concludes that the MAD ECS with a bleed-less air-cycle system (ACS) achieves a higher COP at the cruise phase of the aircraft compared to the traditional bleed ACS, and the COP is increased from 0.22 to 0.52 for the cruise phase of the aircraft. The findings of this research provide a detailed thermodynamic platform useful for advanced ECS architecture and demonstrate the potential of bleed-less MAD ECS to increase aircraft efficiency and contribute to energy-efficient next-generation aircraft applications.</p>