section_path: Electricity generation/Energy density
section_name: Energy density
paragraph_text: Energy density
  
  The energy density of coal is roughly 24 megajoules per kilogram (approximately 6.7 kilowatt-hours per kg). For a coal power plant with a 40% efficiency, it takes an estimated 325 kg (717 lb) of coal to power a 100 W lightbulb for one year.
  
  27.6% of world energy was supplied by coal in 2017 and Asia used almost three-quarters of it.