Homeowner here, but I like to think of myself as being somewhat knowledgeable in matters HVAC, so I will address some of your points. 2story 14.5 yr old brick home in ATL 1st flr 1800ft - 2.5t Carrier AC 90K BTU furnace 2nd flr 1800 ft - 2.5t Carrier AC 80K BTU furnace >I'd like to know how large (square feet) your house is. I suspect they run frequent short cycles. Gas ~ .99 / therm Electric - 9.87 cents/kWh Plan to be in house for 20 years. After ton or reading on this VERY helpful forum, settled on Trane to reduce my options. >Based on some of your following comments, you shouldn't limit yourself to one brand, but rather try to find the best contractor. Difficulty finding contractors willing to do load calc. One reputable owner said customer interview, walkthrough, square footage, count of supplies and returns and consideration of 2 story spaces, windows and 20 yrs exp gets him to the same point as load calc. This true?? >While the above factors are important, he may be lucky and guess the right size, or just opt to replace what you already have, but only by doing a heat calc, (along with his 'expertise', can he be sure. Square footage = rule of thumb. Your cooling loads are likely much more than your heating loads. During the hottest days of the summer, do your a/c's run nearly constantly, and is your house comfortable, humidity-wise? Or, are they running frequent, shorter cycles? Also, you need to know what your latent heat gain (humidity) is. Can't do that by walking around. For 1st flr (system located in unfinished half of basement) 3 ton XLi15 HP on top of XV80 80K BTU At 100% efficiency, the HP would deliver 36,000 BTUs. Why would an 80K (80%)unit delivering 64,000 BTUs be proposed. Highly rated installer quoted the above w/ 4ton blower, adding return to finished portion of basement to promote airflow down there, as we rarely use that space or the 3rd HVAC system. >Are you saying that you have a third a/c serving the basement? These new returns, are there corresponding supplies for the area (are they part of the system that doesn't run?)? 1)Is 4t blower on 3t system good idea? Current is 2.5t As long as the blower, be it multi speed or variable speed, can be set up to deliver the proper airflow, it's not a problem. Maybe he had one in stock. 2)I Like XV80 for dual fuel flexibility and dont see need for 90%+ since HP should handle most ATL heating days. Thoughts? >See above. 3)Is XLi16 worth $500 extra? Dealer says 2 stage makes hard to compare apples to apples w/ XLi15. Says 2 stage offers much greater energy savings and humidity control. >Depending on what your heat loss is, and the size chosen, the HP may not need to run in stage 2. Two stage equipment is for comfort, not energy savings. You still require the same BTUs to heat your house. Likewise, depending on your actual cooling needs, if your HP will run mostly in first stage for air conditioning, it will help in controlling humidity. It is important that a properly matched evaporator coil be chosen. I had considered Trane equipment at one point, but the contractor could not supply detailed info (specs) on sensible and latent capacity of their coils. Upstairs (system in attic) 3 ton XLi15 HP w/ electric strip backup and variable speed blower >Same comments apply from above regarding actual heating needs. 1) ATL winters, 2 story foyer and family room, heat rises makes me think I can do w/o gas upstairs. >With strip heat, you don't need gas. Will I save much in price on variable blower w/o furnace, or should I get the XV80, even though I do not think I will use much gas up there? >In order to make these decisions as to what type of equipment (gas or electric)makes sense for you, you need to know what your heat losses and heat gains (sensible and latent) are. 2)XL16i HP worth extra $500? >Off the top of my head, I would say no. (my guess) 3)Is 4t blower w/ 1 extra return on 3t system good idea? Current is 2.5t >Generally speaking, more return is good. Has your duct system been evaluated and your total system static pressures been measured? I am assuming I should insist on Honeywell VisionPRO IAQ for both? They are an excellent TS and can enhance dehumidification when used with a variable speed blower and combined with other air quality equipment. Also have been told that XV90i no loger offered by Trane. Is it and if so, should I consider it downstairs? That is true. Again, you need to know the (heat calc) numbers to accurately determine which fuel makes the most economic sense as your alternate. Any advice would be appreciated!! Information about wall and roof insulation, make of windows, shading of house, etc., would be helpful. V

giomo I will take a crack at your question. Prices vary between markets and the degree of HVAC competitive forces at work. probably in the 20K range. IMO

Hi, just had a complete system installed yesterday (4-18-2011). I live in N.dallas where cooling means more than heating. cost exactly 7k for everything (negotiated price). here is a list of what was installed for a single story 2000 sqft house. Trane XR13 4 ton AC condenser - 13seer, 14seer with matching system. Trane XR80 5 ton 1 stage with 4 speed blower. New matching evaporator coil with the new R-410A refrigerant. New return and supply plenums, all sheet metal construction with exterior wrapped insulation. New manual air dampers at each supply duct. Added an extra return air duct, grill and filter to double existing volume of return. New drip pan with overflow float switch (cuts off system if drainage gets blocked - keeps the ceiling from getting water damage). New electrical disconnect and wiring (located outside by the condenser). New concrete pad. New programmable thermostat. Did all the work required to rid and clean system of old coolant, hauled away old system and did a relatively good job cleaning up. This new system is so much cooler and has better airflow than the old one and should be more efficient. I really wanted the sheet metal plenums with EXTERIOR insulation and the manual dampers. This should really pay off in the long run for comfort and health. Next time I should just have to replace the AC condenser. Furnace later. All in all I think I got a good deal and I'm pretty sure the work is A+. I paid a little extra for the plenums, dampers and for Trane products. One reason I went with this contractor instead of the others is this contractor continually offered top notch material, construction and products without me having to ask. The others would match the packages and price only after I asked for the better stuff. This really spoke about the quality of work I could expect, and the contractors doing the work matters more than the brand name. But since I could get the best brand name Trane products with top notch quality workmanship, it really was a no brainer. I actually spent just a little more for this company than the slightly cheaper one for the same work.

Arcas, I can appreciate your calculations (I spent a month doing the same thing while also getting multiple estimates from 10 contractors), but after researching I discovered is more than just rate of return from system efficiency. As previously stated there are differences in build quality, controls, noise, and most important installation quality. For your analysis I will assume you include any local utility and state rebates (That reduced a qualifying furnace and HP by $400 a piece where I live or $350 for an A/C). In the OP's case it is the following for VA: Gas Furnace (ENERGY STAR qualified): $250 Heat Pump (ENERGY STAR qualified): $300 There are also manufacturers rebates to account for(although I think that season may be over at the end of June). I will also assume you could care less about noise as you get a good bit more of it in a basic system (I know as it's night and day from my old system to my new one) or the excellence of an Infinity controller in the OP's case (it can control dehumidification in the summer, a humidifier (if desired), tell you when you need to replace your filter, and let you know if something is wrong with the system). A nicety, yes, but some people like to have a better quality and more capable item. Kind of like buying a car. Regardless, Option 2 should include the tax credit as it should be a qualifying A/C system (since you should be able to replace the inside coil for compatibility purposes and 16 SEER should qualify. This is assuming you don't have ancient furnaces). This would drop the difference to only $382 which you would gain back in the expected life of the system. Option 3 doesn't take into account you have a brand new furnace which will not have to be replaced for at least 10-20 years. Unless you have relatively new systems. Either way you shouldn't have to replace them if you drop in a straight A/C since that can be tax qualifying on it's own. (see option 2) You should not assume equal usage either due to varying heating and cooling loads, but I get that it is for simplicity. Option 4: Well, not going to argue costs there as you are getting 4 new systems. The $1500 can be made useful especially if you have good local rebates for high efficiency systems. I have no idea how old your furnaces are, but if they are more than 15 years then it's likely they won't be long for this world. In the OPs case if they keep the furnace and sell in 5-10 years expect to give credit for a new one (I know I asked for credits for systems I knew needed replacement when I bought). As with many things in life there are many factors to take into account(more than I was willing to spend time on), so in the end I suppose the answer must be it just depends...