This research examines the drivers and barriers influencing the adoption of decentralised renewable energy technologies such as rooftop photovoltaic solar systems and consumer battery energy storage systems. Using the analytic network process, expert input from government, academia, and industry was used to prioritise a range of social, economic, institutional, and technical factors in both countries. The results show that while fiscal incentives and stabilised energy prices are common drivers in both contexts, Colombia faces stronger economic and technical barriers, such as limited access to funding and techno-economic uncertainty. Conversely, Spain's decentralised energy transition is primarily hindered by techno-economic uncertainty, challenges related to the electricity tariff structure, and the lack of technical definition and standardisation. This comparative analysis offers novel insights into expert-based priorities across two contrasting national contexts. Based on the findings, it is recommended that Colombia focus on enhancing access to finance and strengthening regulatory clarity, while Spain should refine existing frameworks and simplify technical procedures to facilitate the scaling up of RET adoption. Graphic abstract: (Figure presented.)