I had the same furnace/a-c installed this spring (furnace was an 09). Your price is fantastic. I got the filter and had some ductwork revision for over a thousand more (after rebates, no humidifier and not your model thermostat). I think labor rates are higher here in the Philadelphia, PA area. The furnace can't be beat for comfort, as compared to your old single stage unit. It is important that a heat calc be performed, both for heating and cooling. Also, SEER will depend on which coil is matched to the a-c/furnace. Depending on your particular climate (temperature vs. humidity), a coil that is designed to deliver a higher SEER (larger), may not be optimum for humidity removal. Another word on heating: The Mod gives 13 stages of heat at 5% intervals. Carrier's MVC model has 3 stages and is not a true modulating unit. York's model has 65 stages @ 1% intervals. When modulating, how long does the unit stay in stage 23 before ramping up to stage 24? Is a change in firing rate of 1% really meaningful? The most important factor is your confidence that the contractor will deliver a first class installation. V

Thanks to everyone for your replies and advice! ryanhughes -- No, I did not share sizing info among contractors; they all came to 3.5 tons on their own. I did, however, mention to Company 3 that I already had an estimate for a 90K BTU furnace, so Company 3 guy said, "well, I was going to suggest 80K, but in that case, let's go with 100K." Also, I did let all estimators know that I'm planning to add on 150-200 sf in the next year or two, so they should take that into consideration. baldloonie -- Nope, not much insulation. some was blown into the attic floor in the 70's, so it's (somewhat) compacted now. Otherwise, nothing at the roof, in the crawlspace orin the walls. And yes, lots of windows -- at least those have been upgraded to double-pane. It's been stinkin' hot this year with several weeks of 90+ temps so far... and we're probably in for a few more (it's a dry heat, though ;-)). Winter nights can get into the 30's during cold years. A few more questions... 1. Company 3 also sells York, and I'm looking into the LX series A/C for space reasons (smaller footprint). In terms of sound levels (dB's) nd reliability, what's your take on Carrier Comfort/Performance vs. Trane XR13/XL14i vs. York LX series? 2. Would I be better off with a completely matched system (e.g., Trane furnace/Trane A/C), or can I mix and match furnace and A/C (e.g., Trane furnace, York A/C)? 3. A couple of the estimates I received included the option to add on a higher-end air filter -- Carrier Infinity (Company 1) or AprilAire 2400 (Company 3). Is it worthwhile to do this? 4. I have allergies and pets. Is there a noticeable difference in adding an air cleaning system? I guess the real question here is "are they worth the money?" 5. Company 3's estimate is about $2K higher than the other two. I assume this is due to the higher price of Trane components, the additional fabrication for the sound-attentuation work, and their fabrication of an "accessible" filter box. Thoughts?

"What are the major differences between 14 and 16 seers" 14 SEER units use one single-stage compressor as do most a/c units. They can use the old R22 refrigerant or the new R410A. 16 SEER typically uses a two-stage compressor and R410A refrigerant. A two-stage compressor will run on the first-stage and then shift to second stage if the first stage cannot provide sufficient cooling. The Energy Efficiency Ratio (EER) determines true operating costs and not SEER. What is the EER of the 14 SEER and 16 SEER units? What is the price difference between the 14 and 16 SEER units? I live in Baltimore and recently replaced an old 7 SEER with a new 14 SEER. I have reduced my electricity consumption by 40 percent in July and August '07 versus July and August '06. Best to you.

Mike_home, thank you so much for helping. I agree that most of San Diego County has near ideal weather most of the year. We live 5.7 miles from the ocean, so we're not arid, but not humid most of the time. We've been having some really funky weather what with climate change and all. We have had heat waves into the 90s with onshore flow that were relatively dry and comfortable, but we've also had upper 80s with 80-90% humidity for 1-2 weeks at a time, which is pretty bad but really rare, maybe 2-4 weeks a year. To your questions: the house was built in 2005 and has 5368 total conditioned square feet. Here are the units we currently have: 3.5 ton - upstairs less master (2040 SF, 10 to 13.5 ft ceilings) 2 ton - master suite 606 SF (10' avg ceilings) 4 ton - lower floor (2722 SF, 10' ceilings) The house is 9 years old, current condensers are approximately 3-4 years old, furnaces and coils 10 years old. I have not thought to repair the equipment because it's "working" - you know, turning on, providing cool air, etc., just assumed it was because they were cheap SEER 10 units and therefore not working well, but I suppose it's the BTUs and not the SEER that determine cooling capacity. I'm not convinced four 8 x 14 registers (plus a few small ones for the bedroom and baths) are enough for the 2040 SF main upstairs area (of which 617 sq ft has 13.5 to 18 ft ceilings plus cool air loss down the stairs, I estimate a volume of about 30K cu ft. We also have 4 large windows, a 10 x 16' skylight, and 10' x 22' sliding glass doors. All glass is dual pane and tinted except our new 11 x 5' kitchen window. I believe we need more registers here. The master suite has another issue: in addition to the vents and return in the suite, the master unit feeds an 8 x 14 register to the living room, such that when just using the master unit, unconditioned air blows in from the living room under and around the door, drastically reducing the conditioning effect in the master suite. I strongly believe we need to disconnect the duct leading to the living room and restrict the master system to the master suite. The downstairs remains cool most of the summer and rarely needs A/C, but I suspect humidity may become an issue at times when we're in the 60s and near the dew point. I don't know if a dehumidifier wouldn't be the most cost effective solution rather than replacing the A/C compressor and furnace. I am also in the process of looking into sealing and insulation. They tore the insulation out of the attic to remove walls and install a new flat ceiling on the 2nd floor, and I'm pretty sure the insulation was not reinstalled properly, because even on 80-85 degree days it gets hotter than the outside. Downstairs stays almost 10 degrees cooler and almost never needs A/C use. The garage has never had insulation above it; completely virgin attic space, though the garage is not conditioned space. I believe good attic insulation would significantly reduce our cooling needs upstairs. Thanks again to all those who look and help out! David