Along with the new 80 gallon GeoSpring, GE announced their new ducting kit. It works on all the existing US-made GeoSpring models.
Link:
http://products.geappliances.com/app...a-specs/GVK8HS
Installation manual:
http://products.geappliances.com/Mar...e=49-50304.pdf
Requires 8 inch ducts, unless you use a booster fan (it's unclear what size fan would permit you to run what size duct). You can't cut an 8 inch hole in a rim joist, so this will cause interesting issues for basement installs. I guess you'd have to re-purpose a window.