This work enlightens how remote monitoring of a shallow geothermal energy (SGE) system with minuteresolved data collection can contribute to the identification and quantification of efficiency-related problems. A specific SGE installation located in Tremp (Lleida, Spain), equipped with a vertical borehole heat exchanger (BHE) and a ground source heat pump (GSHP) was analyzed for this purpose. It was found a current average heating/cooling capacity over 10% under declared values of the GSHP equipment. In addition, the influence of part-load operation in seasonal performance was identified. The results were obtained from more than one complete year of data collection. The quality of the information obtained through data analysis was assessed in terms of the datacollection frequency. Weekly averaged data (available for more than 3 years) revealed that the capacity reduction is taking place progressively. Moreover, the seasonal coefficient of performance and seasonal energy efficiency ratio measured at the SGE installation under study were compared with those simulated by the software ground loop design (GLD, v2016). This supported the observations pointing to a progressive decay in performance.