Geothermal energy is a form of renewable energy with a long tradition in European countries, although it is scarcely used in Spain. One of the reasons for this is the poorly studied geothermal potential of the Spanish territory. In recent years, data published on terrestrial gamma radiation and the geochemistry of radioisotopes in rocks have suggested that the radiogenic heat production (RHP) in some areas of Spain is high. In this work, we assessed the RHP by analysing the U, Th, and K contents of the rocks underlying the most important campus of the University of A Coruña (northwest Spain), using in situ handheld gamma-ray spectrometry (GRS) and X-ray fluorescence spectrometry (XRF). Our results provide a good fit of the radioisotope contents and unexpectedly high RHP, compared with average data observed in similar rocks (granodiorite). These results reveal that GRS is a very reliable tool for studying the RHP of rock surfaces, and that geothermal energy can be used in the area (i.e., the studied campus, but also most of the city of A Coruña, as it is built on the same underlying rock) for central heating in buildings using ground-source heat pumps (GSHPs).