Last year I had a new 5 ton Trane XR-13 external unit installed but did not replace the air handler inside. I want to do that now since it is 15 years old and has had mechanical problems lately. A variable-speed air handler would cost about $800 more than a non-variable but seems like a good deal in the long run in terms of value and energy efficiency. Is my reasoning logical? More important, in terms of compatibility of the inside and outside units are there specific things I should be careful to consider in choosing an air handler? Should it also be a Trane and if so what model? Other factors? Thanks very much in advance for any advice you can provide.

You will have to visit the Trane site for information in regards to a match for your outside unit. It is the only place you can really obtain information on the subject with the exception of the .Gov energy savings site.

The payback time for a variable speed air handler far surpasses the actual savings plus if it ever needs repair the price of the module and motor etc is extremely high.

In almost all cases you will have to have a contractor do the work so you might as well work with a local company since they will be able to give you the correct info. I would also suggest you get at least 2 estimates.

Thanks, HVAC for your thoughts. I'm curious to know why people would ever opt for the more expensive variable speed handlers if they don't pay for themselves in energy costs. What are the advantages of a variable speed unit?

They are supposed to save energy but in the long run actually cost more when they break.Most people have no idea what they are buying to start with.