Castellón has one of the least efficient residential stocks in Spain. 96.83% of its homes fall between energy classifications D and G, making it the second province with the worst results in the country, just behind Las Palmas, which registers 97.11%. This situation places the province among the worst in the country in terms of residential energy efficiency.
The cause of this situation stems from a structural problem shared with much of Spain: the enormous proportion of homes built before standards incorporated rigorous energy efficiency requirements. On the other hand, new construction, much more efficient, still represents too small a part to transform the entire housing stock.
The report that supports this data is "State of Energy Efficiency in Spain 2026", prepared by Accumin Intelligence for Tinsa, using information from energy certificates reported to the Ministry for the Ecological Transition. This document provides a detailed view of the state of energy efficiency in the Spanish residential sector.
