This paper highlights the higher annual solar irradiation incident of single-axis N-S trackers installed on sloping terrain, as compared to horizontal ones. Researchers showcase the results of a year-long experiment in which a N-S aligned single-axis tracker prototype was used in Gijón, Spain. The experimental results confirm the trends in the formulas and simulations. Finally, theoretical values for the energy gain for different slopes, at locations over the northern hemisphere between latitudes of 6◦ and 60◦ are provided. These gains can reach values up to 13.5%.