Tiger, Thanks for the information. It is very helpful. I have a two story 2500sf house. The furnace is Bryant Upflow furnace Model number is 383KAV. The nat gas cost is $0.61678 / therm in Feb. and $0.52404 / therm in March. The electricity cost is $0.11877 /KWH. I had an estimate from one dealer. He said I need a 4 ton 13 seer AC. I need Evaporation coil and condensor. He suggest Lennox ac. The model number is 13ACX-48-230. The cost is $3990. Is this a reliable system? How about the price? I think it is kind of high. Does the size sounds right? The dealer did not performance any heat cal, just based on the size of the house. I will have another dealer come in next week. I talked with him on the phone. He suggested to replace furnace with new AC. Here is my question. If I decide to go with new furnace and AC. What brand and model I should consider. I do not need a super efficient system. I need a good reliable system with good efficiency. I may also take advantage of fed tax credit or maybe factory rebate. Thanks

If I did not know better I would swear that this info was about me. In any case I am in the same ship. Last Oct I replaced the accumulator at the cost of $800 and then last Thurs the compressor died. Well I am hard pressed to put another one in as the system is 12yrs old. so now I have a 10seer unit and that is out of date. Seems to me that I am getting a new system. Problem is which one. I am in Mobile Al so the Heat pump is pretty good here. I have 3 proposals. 1- 13seer $4838 Merv 10 filter sys. Or #2 15seer $4990 merv 10 or #3 16 seer 2stage cooling and Air Handler with Var spd blower...$7040. So there is a $2000 diff here and I do not know if I am going to get 2k worth of savings to warrant..Help!!! BTW that is total prices.

We cannot advise you from here on equipment Brand selection. I would get a number of bids. "The quality of the installation, along with proper equipment & duct system sizing are what counts!" Before you select the equipment, size,etc., I would evaluate do everything possible to reduce the heat-gain/heat-loss, make the cost-effective improvements & then do not oversize the equipment. - udarrell Here is a link that might be useful: Sizing A/C for Optimal EER & SEER Efficiency

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...