Housing conditions and energy efficiency Households by main heating system by income quintile per unit of consumption. Unidades: NA ;Central heating;Individual heating;Non-fixed heating system;Other;Does not use any heating system;Not specified; Total;8,9;55,1;17,2;0,9;15,7;2,3; First quintile;5,4;42,9;24,2;0,6;25,5;1,5; Second quintile;6;50,4;20,4;0,8;20,3;2,1; Third quintile;7,9;54,6;17,9;0,9;16,3;2,5; Fourth quintile;10,9;60,5;15,5;1;9,7;2,5; Fifth quintile;13,9;66,7;8,6;1,1;7;2,6; Notas: Income per unit of consumption is obtained, for each household, by dividing total household income by the number of units of consumption. The distribution of persons is taken. Fuente: Instituto Nacional de Estadística