Geothermal and Aerothermal Heat Pumps in Continental Climates: A 21-Year Technical, Economic and Environmental Assessment in Castilla y León (Spain)

The decarbonisation of building heating in continental climates requires reliable high-efficiency electric technologies capable of operating under demanding winter conditions. This paper examines geothermal (GSHP) and aerothermal (ASHP) heat-pump deployment in Castilla y León (Spain) using two explicitly differentiated evidence sources: (i) more than 21 years of accumulated professional and operational experience from over 200 residential installations, for which monitoring coverage is heterogeneous, and (ii) detailed 2025 energy data from three air-to-water heat-pump systems in tertiary buildings. The latter systems yielded annual/seasonal energy ratios between 3.85 and 4.17, calculated from reported useful thermal energy and electrical energy consumption. Because the historical installations were not instrumented consistently, the 21-year record is used as contextual field evidence rather than as a homogeneous longitudinal COP dataset. The monitored tertiary cases are likewise not treated as statistically representative of residential or ground-source systems. The study therefore focuses on the practical evolution of heat-pump deployment, the measured performance of the three recent cases, and the methodological limitations that must be considered when transferring field observations across applications. Economic and environmental considerations are presented as scenario-based context rather than as case-specific measured outcomes.