Influence of cities population size on their energy consumption and CO2 emissions: the case of Spain.

Half of the world population live in the cities. Cities energy consumption, environmental impact, and the opportunities they provide for our planet's sustainability make them attractive for governmental authorities. Any action taken in the cities has immediate repercussions. For this reason, many statistical data are published every year. This paper makes the best use of these data to calculate cities CO2 emissions and their thermal and electric energy consumption. The methodology applied takes into consideration each city size by number of inhabitants and gets results per inhabitant and household. This will make possible to put into practice the right actions to reduce CO2 emissions and to use alternative energy. This paper also defines an index to facilitate and simplify the analysis of results. This study was applied to the case of Spain to show the methodology here proposed. In fact, this type of study has never been carried out in Spain before. With this purpose, the 145 Spanish cities with more than 50,000 people were considered. Results show that cities with larger populations present higher consumptions per inhabitant and household. The smallest the population of a city is, the less energy the city consumes. However, electric energy consumption remains constant regardless of the population size. With regard to the CO2 emissions, results bring to light that the biggest cities produce the highest emissions. Furthermore, comparing emissions produced by electrical sources to the total emissions, it was concluded that the smallest cities produce the highest electrical emissions.