Spatio-temporal diffusion of groundwater heat pumps across Austria: A long-term multi-metric trend analysis (1990–2022)

The transition to carbon-neutral energy systems necessitates the widespread adoption of granular renewable energy technologies, with geothermal heat pumps (GHPs) increasingly recognised for their significant potential. However, their long-term spatial and temporal adoption patterns remain underexplored, particularly for groundwater heat pumps (GWHPs). This study bridges this gap by examining GWHP diffusion across Austria from 1990 to 2022. We integrate fragmented regional data into a unique national dataset and employ a multi-metric, multi-scale approach examining total installations, per capita, and per habitable land area across three geographic units (national, NUTS-2, and NUTS-3). Key findings reveal significant regional disparities: some areas show robust growth, while others experience stagnation or even decline. Nationally, GWHP adoption has increased at an average annual rate of 5.6 % (95 % confidence interval: 3.6–10.4 %). Breakpoints in 2004, 2009, and 2018 indicate significant shifts in adoption trends. Interestingly, regions leading in total installation numbers do not necessarily lead in normalised metrics. This variability across metrics challenges the assumption that a single metric can fully capture regional leadership, indicating a more complex pattern of deployment than previously thought. A cross-sectional correlation analysis further shows that adoption trends are influenced by different factors, including economic prosperity, educational attainment, and climate. Wealthier regions with higher levels of tertiary education tend to have denser GWHP adoption. Colder regions and those with significant primary sector employment show a tendency for lower adoption rates. These insights could inform the design of policy measures which are tailored to the unique characteristics of different areas, helping to promote GWHP diffusion within Austria's renewable energy framework.