Originally posted by mark beiser
However, around here the difference in my cost for a 12 seer ( say 3 ton hp ) would be 400-500 dollars over a 10 seer unit. A thirteen seer would cost even more.
It all depends on your electric rates and cooling demand. In an area with moderat to low electric rates and moderate demand for cooling, a high efficiency system would not pay for the difference in cost during the life expectancy of the equipment.
In the Dallas/Fort Worth area in Texas where I am, the difference in utility costs are much greater because we are paying almost 10 cents a kilowatt and we usually have a very long hot cooling season. Because of that, the high efficiency equipment is a good investment.
Similarly here in the Philly PA area - we have ~5500 degree-days of heating, 1000ish of cooling; temps down to single digits or zero on occasion (Zone 6/zone 7 boundary), and in the Exelon/PECO area electric rates are ~$0.13-0.14/KWHr (in the winter if you have the electric-heat rate you get ~0.065/KWHr after the first 600KWhr). With those rates, I'd believe it will
certainly pay off - our heating costs in mid-winter can be $450/month or more even with mostly high-seer units. (Before we started replacing/reworking things, we hit $1100 in a month).

We installed a 2.5ton and a 5 ton unit (old leaky rambling house with 75 windows), dual-stage carriers - both for efficiency and for comfort/lower noise that a dual-stage gets us. One section of the house (great room) has a ~8-year-old 10 SEER Trane that was left alone. (Yes, our house needs circa 12 tons total, checked with HVAC-Calc and various other people. We have been working on sealing and insulating - we just replaced 4 bubble skylights with modern ones, and insulated (~R25) a sunroom roof (8x25) that was just (real) 2x6's with shingles on the outside, exposed inside (ouch), and two cinderblock 16' long walls that had no insulation now have ~R8 on the inside (plus natural R factor of 12" thick open-core cinderblock).

And what about repairs on the higher eff. units ??
aren't the repairs ( in general ) more costly ??
I think every manufacturer of ultra high efficiency equipment also offers 10 year parts and labor warranties. So for generally less than $500 up front, repairs don't cost you anything for 10 years.
Yes - ours has a 10-year warrantee.

And what is your experience with longevity - do you have any 13 seer systems that have been installed more than 10 years without major ( over $300.00 ) repairs ???
There isn't much in the way of long term track record available.
I have serviced many more 20+ year old 2 speed systems that had no more component failures than a standard system would have had than I have run into that had serious problems.

One last question, Mark, How does a high eff. system deliver more comfort ??
When you get into 16+ SEER equipment, it is all 2 stage cooling. Be it 2 compressors, 2 speed compressors, compressors that spin in different directions, or compressors that unload to reduce capacity.

If the system is correctly sized to match the 2nd stage to the load, the unit will cycle on and off on 1st stage during milder weather, giving much longer run times than a 1 stage system would. This gives more even cooling and increased moisture removal.
When temperatures are closer to design conditions, the system runs constantly on first stage cooling and cycles 2nd stage cooling as needed to prevent the room temperature from rising.

Some argue that the 1st stage has less capacity to remove moisuture, but in most climates, the greatly increased run times more than make up for it, so you get much better humidity removal than a 1 stage system would give, especially during milder than design conditions.

Some make the gross mistake of oversizing 2 stage systems. Doing so virtually guarantees humidity problems. [/B]
I can vouch for the comfort level of 2-stage variable speed fan systems. They're dead silent unless in stage 2 - a big win, especially when it's right below a bedroom (one of ours is) or right above a bedroom/familyroom hallway (one of ours is). We can run them in fan "on" mode all the time with no noise and keep temps more even than otherwise - and people tend to set 'stats to keep problem rooms comfortable.

In the summer, our systems rarely if ever get out of the first stage (I'm not sure they ever do). If we put single-stage systems sized just for cooling (to avoid humidity problems from oversizing), then in the winter they'd be in the Aux heat all the time. As it is, they run in stage 1 in the summer and run long enough for good humidity control, but in the winter you get stage 2 (when needed) and it doesn't need much if any aux until noticably below 30 degrees. We also often run a small (2-ton rated) woodstove in the largest section of the house when the outside temps are 30's or below, and with that going the main system either turns off most of the time or stays in stage 1, even down to single digits. When it's not heating, the fan still runs quietly distributing the heat.

So, as a consumer, I'd vote strongly in favor of high-seer (especially 2-stage) systems for comfort.

Referring to the original message: If the high-seer unit costs double what the low-seer unit does, it's NOT just the equipment cost (unless one is gold-plating the grills). Is one lots of flex and the other all hard ducts? Mastic? How well are each actually sealed? Does the high-seer have nice media filters ($1Kish I think) and the low-seer use cheapo homestore 1" filters? Simple 'stat versus humidistat with setback, etc? Not to say the others aren't overpricing - but look at the prices for the same system setup with different SEER equipment, not contractor and design A versus contractor and design B.