The XL15i is Trane's highest efficiency single stage system and a very nice unit overall. In your case, for a new build, your primary focuses should be proper equipment/ductwork sizing and a quality installation. A properly designed system with good ductwork will help ensure year-round comfort. A 2-stage, variable speed system is an upgrade. The 2-stage system will provide better comfort throughout the home with longer runtimes (hence the need for a properly sized system, single or 2-stage) and therefore more dehumidification. I recommend a variable speed indoor air handler regardless of whether you choose the XL15i, XL16i or XL20i heat pumps (or other). While their summer dehumidification benefits may not be as important to you, one of the main advantages is the blower's ability to maintain a constant cfm (airflow) across varying duct conditions. This means that if the ductwork is less than adequately designed, or if your filter gets dirty and total system pressure drop increases, your airflow won't decrease and the motor will work harder (increase rpm) to meet the required airflow (up to a point, typically 1" external static pressure). This protects the equipment and maximizes performance and efficiency. I would first get a full load calculation (Manual J) to determine equipment sizing, followed by proper ductwork sizing (Manual J). Once you know where you stand, you can make a better decision on equipment selection. If you cover the right bases in terms of system design and installation, you should be comfortable regardless of which type of outdoor unit you choose to install. The XL16i Trane typically runs around 75% capacity on low stage, whereas the XL20i typically runs around 50% capacity on low stage for a greater split. If you decide on a 2-stage system I would look strongly at the XL20i (the system I chose my for home). The dual compressors are outstanding for part-load conditions, dehumidification, and more even temperatures throughout the home.

After reading more carefully, it seems your sizing estimates are all over the place, from 2.5 ton (Lennox), to 3 ton (Trane), to 4 ton (Rheem). A properly done load calculation is necessary to get the equipment size right, especially since you've made changes to your home's structure. Now would also be a good time to have your ductwork balanced so that each room gets the required airflow per the load calculation. Before investing money in a new system, it is very important to ensure your new system is operating at its rated capacity and efficiency.

TXWX 6036E Indoor: TEE3f-39 was told new thermostat Trane matched to system. Yes, I thought that a 3 ton would be large enough. My house is two story. Have three ton system upstairs and new unit will replace 4 ton downstairs. Downstairs consists of large family room/dining combo, kitchen, and one bedroom with bath. Total downstairs approx. 1400 sq. feet. Upstairs about 1200. Usually don't operate both systems at the same time as only upstairs bedrooms are being used. What do you think? Also, in past, we haven't been able to run both systems on heat without tripping multi breaker.

Look at all the numbers. Trane pumps are light on heating, espcially when on an A coil for dual fuel. Also "16" model units may not hit 16 SEER in a lot of matches. Example: most of the matches for the 3 ton 16i show a heat output around 30,000 BTU. Hmmm, where did the other 1/2 ton go? SEER runs 14-15. It does better with TWE air handler though with the new 039 air handler, output again is around 30K. So look at www.ari.org and see output, SEER, EER and HSPF for the unit/coil combo you are choosing. Get away from the 2 stage outdoor unit. That really adds to the cost of the job. That unit on low is effectively about 80% of high, you won't notice a real big diff. Also the dehumidification capability of the 16i on low cool is poor. We just did a job using Nordyne (Tappan) equipment. Warranty blows away Trane's. 95% 2 stage variable speed furnace, 15 SEER R410a heat pump that qualifies for the tax credit so she's getting $500 off her taxes this year. Electronic air cleaner, UV bulb, chimney liner, Vision Pro IAQ, 10 year labor warranty on top of Tappan's 10 year parts and replacement pledge. Our price about what you are paying for the XL16i then take off the $500 tax credit. Oh and she got a new 50 gallon WH too. We also sell American-Standard but encourage people away from it just from the low heat output.