<p>Heat pumps are increasingly recognized as a key technology for decarbonizing heating and cooling, while natural gas systems remain widely used in current building applications. In this context, this study presents a techno-economic comparison of ground source heat pump (GSHP), air-source heat pump (ASHP), and natural gas (NG) systems within an EU-focused framework. To enable a harmonized comparison, the European Union was represented through three comparative climate-zone categories (warm, temperate, and cold), while EU-average economic values were used in the analysis. The comparative assessment was based on life-cycle cost (LCC) and related economic indicators under standardized assumptions. Under the adopted baseline assumptions, in heating applications, the GSHP system offers a cost advantage of up to 36% compared with ASHP systems in all climate zones except the warm zone. In cooling applications, the GSHP system also demonstrates up to 36% lower LCC than the competing configurations. However, to improve comparability across the EU context, the analysis adopts harmonized assumptions, including standardized proxy capital costs and EU-average energy prices. Therefore, the results should be interpreted within the scope of this comparative framework rather than as a country-specific market representation for all EU Member States. Overall, the findings indicate that GSHP systems can constitute a competitive long-term economic option within the EU context, although their higher initial investment costs remain an important barrier to wider adoption.</p>