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