Understanding solar residential adoption in Spain: Insights from an interdisciplinary socio-demographic and energy justice analysis

Adopters of residential solar systems play a crucial role towards decarbonisation by increasing the share of renewables in the energy system. However, a lack of knowledge about their characteristics and motivations hinders the establishment of policies to encourage broader and more equitable access to solar technologies. This study addresses, for the first time, the adoption of photovoltaic (PV) systems and solar water heaters (SWH) in a large sample of Spanish households, emphasising socio-demographic and regional determinants, as well as integrating an energy justice perspective. Results show that the type of dwelling exerts the largest impact on solar uptake, with single-family houses strongly favoured. Contrary to expectations, income does not affect households' adoption decisions. Nonetheless, at the macroeconomic level, GDP per capita leads to significant differences across Spanish autonomous communities. Interestingly, sunnier regions exhibit higher uptake of SWH but not PV, suggesting different drivers for each technology. It is concluded that, in Spain, policymakers should prioritise the dwelling type, ownership status, and education level when setting eligibility criteria for subsidies or financial mechanisms to foster both PV and SWH adoption. For example, tenants living in Multi-Family Blocks who hold, at most, a high school diploma could be a target group.