Terawatt hours to gigajoules converter on this page calculates how many gigajoules are in 'X' terawatt hours (where 'X' is the number of terawatt hours to convert to gigajoules). In order to convert a value from terawatt hours to gigajoules (from TWh to GJ) type the number of TWh to be converted to GJ and then click on the 'convert' button.