[jrref]

The issue of getting parts for the newer variable speed units is something that's passed. Early on this was a problem but these days Variable speed units are common place. If you purchase a new home from the builder a varible speed unit is an option you can get. Many are now being installed because they are the most efficient, give you the best comfort and qualify for federal tax credits. That said, always go with a company who is certified with a specific manufacturer. For example, Sunshine is an authorized Carrier dealer who is large enough to stock parts and has trained staff and the equipment for all these newer systems where as a small company installer who might not have the resources to install and service these newer systems will most likely convince you to get another single stage heat pump because they are the cheapest and the easiest to work on but they will be the least efficient and cost you more money to run them in the long term. Don't be afraid of newer technology since at some point it will be common place. Who ever thought years ago we would have so many computers running our cars? If we didn't advance in auto technology we would still be driving 1965 Chevies that were simple and easy to fix but costly to operate in today's world. Same thing with most technologies.