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