Always tell us what state you live in & major city nearest to you. We have to know what the climate is like where you live, then I have an idea whether it is hot, humid or a dry climate. The square footage of your home & its energy reduction factors, etc. Knowing your location, I know the approximate run-time hours per cooling season, these factors figure into the equipment selection equation. Most every time, the payback is much greater for reducing the heatload & then downsizing the equipment. Additionally, a SEER Rating from 14 to 16 might cool as efficiently with much better payback over its life-span than a 19-SEER or above in your particular climate. It is your money, however, I know the physics & thermodynamics of air conditioning, & the SEER charts should never be used to mislead consumer's into believing they are going to save the differences or have the projected paybacks listed in those ads & brochures. I also recently found the California Research Report on EER & SEER, (report linked on web page below) which supports the position I have held, ever since ultra high SEER has been in vogue. - udarrell Here is a link that might be useful: A/C System Sizing for Optimal EER & SEER Efficiency

caylos a couple of thoughts. I always recommend a minimum of three quotes on same/similar HVAC equipment. Trane has a new offering-the XV95 gas furnace that is 2-3% more eff than the XV90 which is a very reliable model. Does your quote include a new whole house air filter cabinet like the media "Perfect Fit" or "Clean Effects"? Does your quote include a new properly sized refrigerant lineset? It should. Have you had a Man J performed? That is the only professional method of sizing new HVAC equipment. Get it in writing or send the dealer packing. Any ductwork modifications? What size is your home? Has your ductwork been inspected as to size, supply/return balance, leakage test, overall condition, insulation qualities, hot/cold spots in your home? What model thermostat is quoted? There are many intangibles to consider that have not been covered in your post to intelligently answer your question about reasonable pricing? BTW, what is your electric rate? IMO

The biggest problem with HVAC zone systems is knowing when to choose it as a solution and when not to. Some HVAC companies it's about "sell, sell, sell" whether or not it works... there's more money in "sell, sell, sell" --- when it's only about money? So does the comment above mean I do it for free? No. If you think that you are reading things that aren't there. New construction? best to choose separate systems 9 times out of 10. In order for a zone system to work, you have to know what you are doing. Most HVAC companies staff (the techs they send you) are 20-30 year olds. How much practical experience could they possible have? It's best for HVAC zone systems to be an elegant solution. A HVAC zone system is a tool in the tool bag. Not all homes are suitable for zone systems. Some homes there is no other way, and in some cases complications to those problems will make an HVAC zone system design possibly more prone to problems. You have a problem now, do you want more problems. These decisions among others are decided "in person" --- so considering that becareful what information you decide upon from the internet. Just because it's here doesn't necessarily mean it's true. That said: Depending on equipment level chosen, how many different floors you have in your structure, how much room you have available... will all be factors that make you decide one way or another. From there it's in your best interest to pick a contractor that is skilled: especially when it comes to HVAC zone systems. (there's a lot of garbage out there.) (click to enlarge if necessary) I service the Katy, Texas area.

Sizing can be less of an issue when you have multiple units. Because each unit is controlled independently, provided of course the unit itself is not over sized for the area in which it serves resulting in excessive short cycling. In your case 3 ton plus 2 ton isn't necessarily equal to 5 tons of cooling... unless you drive those thermostats really low. By having two systems with total capacity of 5 tons (which, most of the time this would be oversized for a 1700 - 1800 sq ft structure) has a few advantages. 1. You have the ability to use one system only during low heat days or set the opposing unit higher. The unit set higher only runs if load conditions warrant.... meaning if it's not hot, the thermostat controlling the unit does not call... the unit can not run without a call... 2. Utility bills can be much less... because you rarely use both systems at the same time. You run the bedroom system when you sleep, the other when you're awake. If you have a home office in one the bedrooms you may need to rethink things a bit. 3. Extra capacity for when it's hot out. When it's hot you have the capacity to cool the home. (even while entertaining guests --- additional people add heat) Remember heat waves come, heat waves go... a so call 'properly sized' AC system is essentially properly sized roughly 10% of the time... especially if that system is a single speed AC system. Alot of people I come across like to sleep cool. So for that reason I doubt I would change the configuration of the space. Once you realize what you have, the choices you make are mostly budget type concerns. Essentially a set up like this runs like a 2 stage system. This kind of subject is above the pay grade of many... choose your contractor wisely. I service the Katy, Texas area.