Like the OP, we also believe we need a new furnace/AC and have some questions. I also live in the South, but not as far as New Orleans. I am in NE Georgia where summer temps are in the 90s with similar humidity and winter temps can get down into the teens although rarely. The last few weeks, we have seen lows at night in the 20s and daytime highs in the 40s. My husband and I bought our split-level 1979 house this summer. The A/C works OK (original 1970s GE model), although our electricity bills were high ($350/mo.) and air-quality was poor. We believe there is mold in the ducts (plenum was moldy) and plenty of dust also. The gas furnace is also the original GE model and the HVAC guy could not get it to work. Apparently the transformer is shot. There is also rust and possibly carbon deposits under the furnace, leading us to believe the heat exchanger MAY be cracked. At this point we are leaning towards a whole new system, with new ductwork. Is it worth getting a second opinion on the existing ~30 yr old furnace, or should we start looking at new systems? We had problems with high humidity and mold in the house this summer. In addition, I have allergies and asthma, so I am concerned about air quality. I am a stickler for checking and changing the filters regularly, esp. with 4 cats! If we get a new system, should we go for a gas furnace, heat pump or dual fuel? The house is about 1700 sq. ft., split level, with R13 in the walls and single pane windows (we would like to upgrade to Energy*). The main living area is above the enclosed crawl space (under-floor insulation of R15) and the bedrooms are above the garage (currently uninsulated, but looking to put R15-R30 there). All ductwork runs under the floor and is currently easily accessable. We are paying about $0.85 a therm for gas and $0.09 kWh for electricitry right now. I would really appreciate your ideas and insight. Shivering in Georgia!

I'd be willing to bet that a 3.5 ton unit isn't going to cool a 2700 sf house adequately. Also 14.5 SEER won't qualify for the $1500 tax rebate. Needs to minimum 16 SEER, or 15 SEER for a heat pump, and must be puron (R410A) not freon (R22). My R22 ac died last week (coils leaking)--I'm getting a puron system. My house is also 2700 sf, and the current unit is a Trane 5 ton split system heat pump and has kept me super cool (Florida). I may go to a 4.6 ton Carrier 16 to 19 SEER heat pump split system, but certainly no lower.

GoTerps let's look at each system's numbers. option #1 3929268 Active Systems XC14 SERIES LENNOX INDUSTRIES, INC. XC14-024-230-02 CX34-25+TDR SL280UH090V36B* 24000 13.20 16.00 option #2 3929121 Active Systems XC14 SERIES LENNOX INDUSTRIES, INC. XC14-030-230-03 CX34-31+TDR SL280UH090V36B* 29000 13.50 16.00 option #3 3656259 Active Systems COMFORT 16 PURON AC CARRIER AIR CONDITIONING 24ACC624A**30 CNPV*3014A** 58CV(A,X)070-12 23000 13.00 16.00 1 option #4 3656288 Active Systems COMFORT 16 PURON AC CARRIER AIR CONDITIONING 24ACC630A**30 CNPV*3117A** 58CV(A,X)070-12 28400 13.00 16.00 1 all qualify for tax credit. three observations. 1.The Lennox furnace is oversized and should drop down to the 70K model. 2.It is important that lineset be sized correctly whether you select 2 ton or 2 1/2 ton condenser. Flushing is acceptable practice but refrigerant lineset size must be correct. If you elect the 2 1/2 ton condenser, it is unlikely that old lineset will be correct size 3.I do not like thermostat selection for these quotes. I would like to hear from Ryan's ideas/suggestions on this. I do recommend a good 4-5" box filter cabinet. I would not put down more than 25% upon contract acceptance. now to the fuel comparison between electric vs nat gas. to be fair, I will use 50 therms mthly usage to better average your nat gas mthly base charge. Cost per 100,000 btu of useable heat Heat Pump with COP of 2.75 $1.15 Nat Gas Furnace 80% eff $1.81 you can readily see that a HP above temp balance pt is the less expensive choice to heat your home. Keep in mind the main reason for the large difference is the 80% eff furnace. yes, if operating costs are important to you, then HP operation would save you some $$s. ask dealer for option on HP condenser version if interested. IMO

Baseboard electric heat is one of the most expensive types of heat. Certainly not attractive to renters if they are paying utilities. Every homeowner should know about their existing HVAC; age, brand, model, size, and efficiency. If you don't know, then find out. Post your electric and nat gas rates. Post back. IMO