After jumping through these hoops last year, I have some simple advice:
- Pretty much all the units for sale these days are about the same as far as performance and quality. For a given efficiency rate, choose the cheapest you can get...which is usually a Goodman.
- There has been so much consolidation in the industry that there are only about a half dozen companies making the top 15 brands. For example, carrier, bryant and payne are all made by the same company. American standard and trane are made by the same company and identical except for some cosmetic packaging. Goodman used to make amana, some whirlpool and maytag units but I think they spun those off.
- Dont get sucked into paying a lot extra for more efficiency with fancy cost savings charts. The difference in actual electric usage between a 16 seer air conditioner and a 13 seer isnt that much. If its a $300-500 difference, its worth it. If its $2000, its not.
- Given that you live in FL, consider a heat pump instead of a traditional furnace/air conditioner. Heat pumps both heat AND cool, and a higher efficiency heat pump can be a good investment in a climate that doesnt have severe winters.
To simplify it as much as I can, buy a Goodman, make sure the installer is factory authorized, and make sure their quote includes a transferable ten year factory parts and labor warranty. Every manufacturer sells the latter but the installers all try to sell you some kind of hybrid warranty where the installer does the labor and there is some level of parts warranty that may or may not be transferrable.
You'll pay less, if theres a problem with the install its on the manufacturer to make it right because they authorized the installer, and if anything goes wrong down the road or you come to dislike the company you paid to install it, you can transfer the warranty to another service provider. Everyone services Goodman, parts are readily available, and about the only difference between the Goodman product and everything else is that its a builders product with no marketing and advertising.
Lastly, your house size only has a little bit to do with the sizing of the unit. How high your ceilings are, how much insulation in the walls and attic, and how many windows you have and what type they are have more to do with the unit size needs than square footage. Your contractor can do what is called a "manual J" calculation with all this information plugged into a piece of software to tell you exactly what you need. Too big is not good, your unit will cycle more and be inefficient. Too small is not good since the unit may not adequately cool.
Chances are the unit thats already installed in your house is the right size, providing its doing the job and giving you the right level of comfort.