National Defense Net Zero Review Act of 2020 This bill requires the Government Accountability Office to report on (1) the progress of the Department of Defense (DOD) toward reaching net zero energy goals, and (2) DOD operational energy usage. The bill also requires DOD to (1) annually report on total emission levels for each of the ten preceding fiscal years, and (2) develop a master plan for achieving DOD-wide net zero for energy, water, waste management, and emissions.