The original installer was also the one who done the upgrade. He thought the unit was sized enough with the additional 480sq. ft. addon. I'm not sure if I want to go to the expense of putting in a new system when we may not even be living here in the next 2 or 3 years. I heard that a new regulation was going into effect in 2009 and was told it would be better to wait until then if I decided to replace it. Not sure what the new regulation was though.