Researchers at the University of the Basque Country (EHU) have explored how a combination of photovoltaic energy and heat pumps could be used to carry out the energy retrofitting of social rental housing. Published in Building and Environment, the Basque Government’s Zero Plan was used as the basis, and the technologies that the European Union is keen to promote were assessed. The buildings in Araba-Álava were generally found to offer the greatest potential for implementing the system.