If you can afford the 90%+ furnace, this would probably be a better investment. As to the variable, IMO, it has a purpose, but it is not for everyone. When the fan is not running at high speed (which is most of the time) you do not get rated cooling. If you do not get rated cooling, it will run longer. The outdoor unit, which is the more expensive energy user, will cost more to operate. It will need replacement quicker. During hot days, it will loose efficiency it it runs too long of cycles. I live in what I consider a hot climate. The temperature is over 100 degrees about 100 days of the summer. If the system does not cycle, it will fail quickly. Service will cost more.

Thanks for the reply. I'll probably go with the 93% and the tax credit will help soften the blow.

Steelnuts,go with the variable speed if you can afford it.It will save you money and keep you more comfortable.The 2 stage is a very good setup.My climate is perfect for variable spped and 2 stage equipment.We are hot and humid many days of the summer.Bob Brown is from Africa at 100 days of over 100 degrees.

It does depend on where you are located. In Phoenix you would not would not recover the extra cost of a 95% vs 80% efficient furnace.

Variable speed is also dependant on your location & the humidity.

As usual Bob Brown has distorted the truth. His area does not have 100 days per year of over 100 degrees.

I was going to choose the 2 stage over the 2 stage variable, but my understanding is that the variable circulates the air throughout the whole house so there is more evenness in temperature. We have a cold downstairs and a very warm upstairs. I am hoping this will help in the winter and the summer.

Not only does the area have many 100 degree days, many years there are 100 continuous days. This means every day for 100+ days is over 100 degrees. I don't know who you are or what you think you know, or even if you are old enough to shave, but you are very misinformed if you think that I am wrong. Last year we probably had about 120 days over 100 degrees. I don't know if we did the 100 continuous or not, because it is not infrequent that this area does this. M13, since you are from NC, why don't you listen and learn from people smarter than you.

The main purpose of the variable speed system is in humidity control and staged cooling/heating. A VS (variable speed) system can remove 4 times the humidity than a regular system.
The VS is not a corrective device for insufficient ducting or to correct the delema of two story "upstairs hot/downstairs cold" conditions.
A system designed to run a little longer is actually more efficient in some areas of higher humidity, as it allows more removal of the latent heat, and you'll be more comfortable at higher temperatures and as a result be able to set the system at a higher temperature than normal.
Studies have shown that a systems life is shortened not by running more continuosly, but the strain of cycling (starting and stopping) too often.
The VS, set in the enhanced mode will begin running at very low rpm for the first minute, go to 3/4 speed for another 7 minutes, then to 100% after that. A properly designed system will rarely see 100% speed until outdoor temps are steadily high. *Some two stage systems will operate differently.
If your area is in a dry climate, humidity isn't a problem, however the VS will still be the better choice for sure. Look for a good 10 year parts and labor warranty- it will be a good investment with this type system.
Also ask about a 4"-5" media filter system (HEPA)- honeywell, April Air and others make such a filter system. Installing such will not only help with the indoor air but keep the new system clean, maintaining efficiency and ridding one from having to clean the indoor unit.

Bob,

If you would ever do just a little research you might not make so many ignorant statements.

See this webpage for the data pertaining to 100 degree days. From 1899 to 2004 DFW only averaged 16 days per year over 100 degrees, the most was in 1980 when they had 69 days over 100 degrees, and the highest consecutive days were 42, also recorded in 1980.

http://www.srh.noaa.gov/fwd/CLIMO/dfw/annual/d100info.html

Mike13... I posted those same numbers for Bob a couple of months back, when his fact-addled, thought-processor once again overheated and he spouted that DFW 100 days 100F piece of truthless gibberish. He ignores it. Does not compute. Needs water-bath to operate!

steelnuts... your profile says you are zone 8. If you are in a zone 8 like it is in north Texas, then a VS blower will help immensely with humidity control and comfort. The gist of it was explained by daddo. In a primary cooling zone, spend the money on the best cooling you can get, get a VS blower and you can lessen the furnace efficiency side a little. A homeowners, that's what we did for our new home and we do not regret it.

And, ignore Bob.

DB,
I guess you have finally tipped you hand. You cannot possibly live in Dallas, or you are living in a different world. Kinda like your claims of electricity prices by TXU in Dallas. Just what planet do you live on.

As to the quoted report, that is an average over many years. If the average is designed to promote tourism, it will be skewed to the best advantage. You are correct, we have not had 100 continuous days recently, much to my suprise. We have had many years of 100 days or more.

The stastics posted on that site are AVERAGED over MANY years. Get real. Any average of anything makes the numbers look either good or bad, depending on how you read the data. BTW the average is not indictive of the area. It is taken probably 100 ft above ground on a flat plane of 18,000 acres. (DFW airport) If you were to use a laser thermometer and measure the surrounding surfaces, measure the sun, then measure the ambient, you would be surprised at the differences.

As to DB, he has shot his wad once too many times. Seeing is believing. I always heard that programmers lived in rubber padded rooms. I guess you never go outside or pay the electric bill.

Bob, Bob, Bob... ye canna hold 'er no more... she's gonna blow, due to a pileup of head-waste!

There you go again, posting rubbish. Here it is for you again -- put on glasses, see link, Bob.

Most consecutive 100F days: 42 days, 1980 (Jun 23-Aug 3)
Most 100F days: 69 days, 1980

All the other years are less.

And that's going back to 1903 Bob, which is likely the year you first started spraying water on copper coils.

Parts is parts. Kirk out.

Here is a link that might be useful: Dallas/Fort Worth - Annual and Consecutive 100°F Days

Bob,

I must say you are good for a laugh. I don't know if you make these ignorant comments just to get a laugh or if you are really that ignorant. What is your definition of an "average"?

"Most consecutive 100F days: 42 days, 1980 (Jun 23-Aug 3)
Most 100F days: 69 days, 1980

All the other years are less."

Those numbers are NOT averages. The only "average" I gave above was the statement of "From 1899 to 2004 DFW only AVERAGED 16 days per year over 100 degrees,".

Since the factual numbers came from the National Weather Service I don't think they are biased to promote tourism.

And given that you can't even keep a friend of yours HVAC equipment running for more than a week, I certainly would not compare your methodology for computing temperatures to be superior to the National Weather Service.

Posted by Bob Brown...

"I have a problem customer that is an old friend. I spend too much time working on his 2- TRANE systems. Both the 12 year old unit and the 4 year POS. They seem to take a dump weekly. I am the last of many Techs to work on the systems. I first got involved last summer when the new system would not work. I have not been able to keep that system working for more than 1 week at any time."

I have a problem customer that is an old friend. I spend too much time working on his 2- TRANE systems. Both the 12 year old unit and the 4 year POS. They seem to take a dump weekly. I am the last of many Techs to work on the systems. I first got involved last summer when the new system would not work. I have not been able to keep that system working for more than 1 week at any time.

I forgot to mention that the NWS has a specification that requires temperature sensors to be mounted 5 feet +/- 1' above the ground, not 100 feet as you suggest above.

http://www.nws.noaa.gov/om/coop/standard.htm

You guys are wasting your time with Bob.He does not understand how a airconditioner works much less a variable speed fan.He gives homeowners on here so much false information.

You guys and Bob (the "Other" Bob) are, indeed, good for a laugh...which I needed. Thanks.
I am working on my second A/C installation in pretty efficient houses. The first installation was done by an A/C contractor who sized the unit 100% too large - 4ton when it should have been 2ton), single stage. In Panama City, FL and its environs, humidity is a big problem. So, this time, it will be the proper size, and definitely 2 stage, variable, since this is the best way so far (other than possibly the Lennox deal where there is a dehumidifier A-coil added to the air handler) to deal with humidity. Also, of course, all the other good reasons listed by the guys above.

Bob: Don't let mere facts get in your way; don't give up. You may not be "winning" - Heck, you may not even be breaking even, but if you're right, you're right! Right?