I just had the 30 amp Siemens installed - http://www.amazon.com/gp/product/B00MFVI92S?psc=1&redirect=true&ref_=oh_aui_detailpage_o04_s01
$550 for the unit, $750 for the install (panel maxed out so needed a panel expansion).
My only complaint - cable is a bit short - get a longer one if you can.