The construction industry is responsible for 36% of the European Union's greenhouse gas emissions. The main goal of the EU in the last decade has been to boost energy efficiency and expand the use of renewable energy in buildings. Ground-to-air heat exchangers may be a solution to reduce the use of primary energy in buildings from nonrenewable sources. The study in this paper deals with an evaluation of the heating and cooling energy potential of a ground-to-air heat exchanger (GAHE), serving a pilot energy-efficient building in Romania. The research follows a comparison between the experimental behavior of GAHE, evaluated based on measured outlet temperatures for two full years, and theoretical behavior, assessed using two computational models following EN 15241:2007 (Model 1) and EN 16798-5-1:2016 (Model 2). A comparison is made between the energy potential calculated using temperature measurements and the energy potential determined based on calculated outlet temperatures using the two models. The assessment is performed as well for conventional climate corresponding to the building location.