This is (unfortunately) usually shown on television in a heavily cut 105 minute version. The complete three-hour version can sometimes be seen on Turner Classic Movies

After its original "roadshow" engagement in 1947, where the full 173-minute version was shown (with an intermission), "Mourning Becomes Electra" was cut to 121 minutes for the remainder of its theatrical run. This version is not available for television, but does exist in 16mm prints.