pricing vaires, mary. you may want to look at trane's sister company american standard, if trane pricing is too high. same stuff..different label. I find 15-17 SEER to be good efficiency. good savings over minimum efficiency allowed by law..decent payback period. pairing 15 SEER (for example) with a variable speed air handler unit will give you control over humidity. this upgrade will cost about $500-$700 depending on costs in your area. but it is worth every penny because of removal of humidity that it provides. In La. like Fla. high RH(relative humidity) is what makes us uncomfortable when summer temps are 90 degrees & RH is 90%. controling RH to maintain 50% RH is what makes us comfortable. when RH is lowered, the air is colder, so t-stat can be raised and you still be comfortable. staging the heat strips will save you $$ in heating season by not engaging full stips unless needed. most of the time you'll be using heat of heat pump, not emergency heat. while 2 tons for 1,008 sq ft is a lot of a/c, the cost is the same for 1.5 tons as it is for 2 tons. at the end of the day...most companies will sell you 2 tons. to overcome this oversizing, you need the ability to slow the air speed, so that relative humidity is controlled. thus the variable speed ahu. I'm in a small home also. Over the years I've learned a lot about hvac, due to the type of work I do. when I got ready to put a central system in my house (980 sq ft) I installed a two ton heat pump, 15 SEER with a variable speed air handler, staged heat strips. in the summer..my utility bills are $60 at hottest months (aug, sept) winter...$40. don't think emergency heat has come on this mild winter at all. I planned my system to remove humidity, and have been pleased with the success. in August my indoor RH was 50-55% even on rainy days. having gotten a steal of a deal on a whole house dehumdifier I can lower RH to 40-45% and turn temp at tstat higher. If I hadn't gotten the dehumidifier at such a good price..I'd still be ok, because I planned to dehumidify with vs air handler. without dehumidifier RH is still in acceptable range & comfort is great! lowering the speed of the air removes more humidity and air gets colder. cold..in august..heavenly! don't get hung up on name brands. for each big name is a sister company with same equipment with different label. shop around, get bids that give you good...13 SEER better 14 SEER and best...15-17 SEER bids. get at least 3 bids, then compare. tell hvac companies of any issues...excess dust, hot/cold spots, condensating supply grills etc while they bid your job. then share this info with us, & we will advise you & explain any questions you have. make sure they know that all ducts are to be mastic sealed...not duct or foil tape. duct leakage is a huge problem that isn't often addressed. if you are paying to condition the air..it should all come inside the house.. not leak out in unconditioned space. install trumps brand in my book. making sure that ducts are mastic sealed, and in good shape is often over looked as is the air sealing of return. I test homes for air leakage & ducts for duct leakage, so knowing how much these things leak..and how much it costs for these leaks..it is a worth while investment to seal them, this type of sealing is a quick payback, inexpensive materials, and noticable improvement to do these types of sealing. best of luck.

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.

I had a similar situation identical to your planed build 2 months ago for an existing 1995 home. My first recommendation was a separate system. The second was a dual zone system, and reluctantly gave a third recommendation of just ducting the basement off the existing furnace. I agree with David Cary about a separate system for the basement for many of his reasons including my own I told the other guy about , like giving the basement it's own independent return system to reduce sound transmission to the upper levels and odors down stairs. not to mention the simplicity, convenience, and redundancy of a back up if one heater breaks down in the dead of winter at midnight. The unit for the upper floors can be smaller saving a few bucks on the furnace, which can be put into the cost of the second separate system for the basement. The similar house I mentioned was 2400 on two stories and a 1000 sq. ft basement where the owner also worked from home. I did a quick load calculation and determined his new (2017) furnace of 60K Btu's wouldn't carry the basement load and pushed the separate system or replace the existing with a 80 to 90K furnace, he didn't believe me and had a few other people out. They all said the 60K was to small, so he had it replaced with a 80K and duct work for the basement without zone control for $5600. He's still going to freeze his feet off down there this winter..... and won't even be able to kick himself for not taking my offer to put in a separate furnace with duct work for $3800.