Gigawatt hours to kilojoules conversion calculator shown above calculates how many kilojoules are in 'X' gigawatt hours (where 'X' is the number of gigawatt hours to convert to kilojoules). In order to convert a value from gigawatt hours to kilojoules (from GWh to kJ) simply type the number of GWh to be converted to kJ and then click on the 'convert' button.