This study explores Dutch homeowners' intentions to adopt shallow geothermal solutions for the energy transition in existing buildings, using the Theory of Planned Behavior (TPB) as a theoretical framework. Through a mixed-methods approach combining qualitative elicitation interviews with 20 homeowners and a quantitative survey of 800 representative Dutch households, the study identifies key psychological and socio-demographic factors influencing adoption intentions. The findings indicate that approximately 33% of surveyed homeowners express intention to adopt geothermal technology within the next five years. Structural Equation Modeling reveals that attitudes toward geothermal technology and subjective norms significantly influence adoption intentions, while perceived behavioral control has no significant impact on intention. Economic benefits and environmental protection emerge as the strongest attitudinal drivers, with uncertainty about investment payback periods acting as the primary barrier. Normative influences from environmental advocates, suppliers, and community members also strongly shape adoption intentions. Among socio-demographic factors, higher energy cost-to-income ratios, higher income levels, and homeowners’ association membership positively influence adoption intentions, while age shows a negative correlation. These insights provide evidence-based guidance for policymakers to develop targeted interventions addressing specific psychological barriers experienced by different homeowner segments, potentially accelerating the transition to renewable heating systems in the Netherlands' existing housing stock.