Abstract The current study presents the results obtained from evaluating 70 health centers in Extremadura (Spain), after researching the morphological and functional parameters that have a greater influence on sizing such buildings as well as the empirical relationships with their energy consumption and emissions. Results have been compared to energy audits conducted over the 2005–2010 period. A mathematical formulation that allows efficient quantification of the optimal floor area of health centers is proposed. It also forecasts their annual energy consumption, which can be used as a reference for future projects planning and as an indicator to assess energy management of such buildings. Optimal sizing of health centers is determined based on the health services provided, by optimizing energy consumption and minimizing greenhouse emissions to the atmosphere.