Where do you live? How old is the furnace you're replacing? What are the age, construction style and size of the house? Where is the current furnace located?

You can get high efficiency single stage furnace with high eff blower motor, 2 stage high eff furnace with var speed blower motor, and high eff modulating furnace with var speed blower motor, all 95%+ gas eff rating. That is the way to go. There is no evidence that they are less reliable or prone to break down. Good installation is everything. What size home, what size is existing furnace, and what is your location?

IMO

I respect and enjoy your contributions, tigerdunes, but you may be premature with your suggestion. In my area, with relatively short and mild temp heating seasons, there is no payback from the added installation and purchase cost of a >80% unit. Or, so I was told recently by 3 well regarded HVAC contractors bidding on a replacement of my two-system heat and AC equipment. All three said, in essence, "we'll put in whatever you want but you'd be wasting your money".

Do you disagree, is your experience different?

Speaking only for myself and my own situation in coastal California, I did weigh the pros/cons and it was a short list- what advice I received from experts (the qualified contractors) and my assessment of cost vs benefit. All answers were the same, it wasn't worth it and it wasn't a close call money wise. What else was there to consider?

Thank you all for your help! I live in Washington State, mild winters, but we do like the house warm. The house was built around 1960, I would say mid-range quality and insulation, about 3000 square feet. Our old furnace is about 15 years old, and keeps failing bit by bit (as in every other month or so another part breaks), so we are thinking it is probably time for a replacement. I imagine that our contractor will recommend a high efficiency furnace, but I am worried that this technology, plus all the other bells and whistles like variable speed blower motor and two stage valves is going to be more repair-prone than a more basic type furnace. I am thinking that a couple of repair calls will nullify all the savings you can get from saving gas with a high efficiency unit..

I have a high efficiency modulating furnace (Rheem) put in in 2006. It has worked well, nothing beyond standard maintenance checks It replaced a 30 year old furnace so who knows what the efficiency was there; but my bills dropped so much the gas company came out 3 times to check the meter. Of course, in a colder climate than yours, ruko37.

As I recall, getting the right size not only for your square feet but also number of windows, insulation etc is very important to continued high performance of the furnace.

I guess your decision (80% vs95%) is rather like when I was trying to decide whether to buy a Versa or a Prius. I did the math--how much I drove, how much gas cost and could cost in the future (I assumed more), the gas mileage of the vehicles, to calculate how much I might save with the Prius; then compared to the price difference of the vehicles. In that scenario, even with gas pushing $4, the Versa was much more cost effective for me. You need to do a similar calculation. If the difference is small, go for the higher efficiency.

How much does it currently cost to heat your house? Once you have that information, you can estimate the potential savings and make a decision.

Your new furnace will likely have a 10 year parts warranty. You may also be able to get a 10 year labor warranty.

3 considerations:

1. Cost - High eff will be more expensive to buy and install (see 3, below) and you may or may not break even on lower fuel costs.

2. Reliability - they should be equally reliable.

3. Installation. 80% should be a simple replacement install. High Eff will require different venting and condensate draining considerations. Condensate freezing in winter may not be a major consideration if your climate rarely gets below freezing but horizontal PVC venting may be an issue. Ask your contractor questions before you make a decision.

I will add that getting the capacity of the replacement furnace is more critical with high efficiency. If it is sized wrong, you can end up paying more for a furnace that never gets you the efficiency that it is can provide negating any savings that you might expect.

Comfort is also an issue. A variable speed blower and modulating burner can be quieter and provide more even heat (over time) dues to longer and lower burn cycles.

I will leave this thread not before stating that homeowner should purchase a furnace correctly sized regardless of nat gas eff (80 vs 95+ eff) with minimum of a high eff blower motor, not a conventional PSC blower motor. Much quieter not to mention the energy savings both heating and AC. Don't confuse furnace gas efficiency and blower motor efficiency-2 entirely different issues.

IMO

Please look into energy efficiency programs that can subsidize installation of higher efficiency equipment including the high efficiency blower and higher efficiency combustion.

I just wanted to thank everybody who posted on this thread for your help!