are newer furnaces more efficient?

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On Wednesday, January 28, 2015 at 6:15:11 AM UTC-5, philo wrote:

Similar here with my 93% Rheem. There isn't anything exotic there that I can't fix myself.

+1

That helps too, same here.

I got the fed tax credit back in 2010, which was ~$1200. Those credits reduce the cost substantially and there isn't but a few hundred dollars difference in the cost of a 93% furnace compared to an 80% one.
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On Tue, 27 Jan 2015 18:07:27 -0500, Curmudgeon

+1
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CRNG wrote:

Hi, My furnace came with 10 year P&L warranty plus heat exchanger is on life time warranty.
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On 01/28/2015 12:59 PM, Tony Hwang wrote:

I'm also in the camp of I'd have to see actual data that shows a negative rate of return over a longer period to believe it true as a general statement.
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On 1/28/2015 2:03 PM, dpb wrote:

My 16 year old furnace gets an annual cleaning and inspection as part of an annual maintenance agreement, for less that $250 a year, that has saved me many dollars on several occasions when parts went sideways.
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On Tuesday, January 27, 2015 at 6:07:34 PM UTC-5, Curmudgeon wrote:

I'd be happy to see data that supports that. There are a lot of people with fuel bills of $1500 a year. If they save 20%, that's $300 a year. In ten years, it's $3000, about 50% more than the cost of the furnace equipment to begin with. I replaced my 27 year old nat gas furnace 4 years ago and have been saving 40%+, Ed reports similar with a boiler. I'm saving about $300 a year. The most costly repair, would be the heat exchanger. All the systems I looked at, the heat exchanger was either warranted for 20 years, lifetime, etc. Not saying you won't have to put some money into an aging furnace, or that a high efficiency one doesn't have more parts that can fail, just that I haven't seen any real data to support that it's going to wipe out staying with a lower efficiency furnace.

Yes, there are more safety devices on modern high efficiency furnaces, so there is more possibility of one failing. But I also wonder how many safety switches there are on a new 80% furnace now too? I've got 4 years now with a Rheem 93% furnace, not a single problem.
This year was another $610 for a draft inducer.

If she paid $610 to have a draft inducer installed, I'd say the more likely problem is that she has a service company that is screwing her. I'd also point out that a lot of stuff today doesn't last as long as it used to. I think in many cases folks are comparing the lifecycles of 40 year old furnaces to modern ones. I'd be surprised if a new 80% furnace lasted as long as one did bought in 1970 too. In other words, you have to compare the problem rate of a new 80% with a new 93%+.
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On 1/28/2015 8:53 AM, trader_4 wrote:
s after the furnace is 10 years old or so.

I was skeptical when the advertising said you can save up to 40% on fuel use. I figured if I save 25% to 30%, I'd be happy I kew what my oil consumption was the the past couple of years so I had numbers for comparison
After the first year, I calculated the oil use based on degree days. At www.degreedays.net I was able to get the historic data also. I was pleasantly surprised to see that I came very close to the 40%. I even contacted Energy Kinetics, makers of the System 2000 boilers. They did their own audit and concluded I save 39.2%.
In my case, the old boiler was about 30 years old and on the way out soon so I had to do something. It was also good timing with Federal energy credits, state rebate and state 0% financing. It would have been foolish to do nothing and pour money up the flue.
So far, it has been trouble free, no repairs. Once last winter I had to cut the power, let it restart and it has been OK since.
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trader_4 wrote: ...

our experience was that within 12 years the heat-exchanger went and even while the company did replace it we still had to spend quite a bit of money to do that. we also had a lot of problems from the ignition system. whatever part it was they were getting was coming from Mexico and it failed each year. finally we asked them to find something else and it hasn't been any trouble since.
our heat costs run between $600-1200/yr on propane (normally the thermostat is set at 58-60F). i think our unit is rated at 95% or so. 98% would have cost us about $500 more when we replaced the exchanger. we've also had to replace the fan.
i sure wish this place had been set up for more passive solar as right now this mid-winter cold day the sun is shining nicely and we could be avoiding some of the expense of heating (for hot water too).
songbird
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Pico Rico wrote:

Natural gas in the mountains?
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yes.
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Pico Rico wrote:

I put in a coleman THE about 25 years ago and the efficiency was 90%. This unit was inexpensive (actually designed for a housetrailer, but it was big enough for our house). I think the trick was they passed much more air through the heat exchanger. It needed no chimney, but the air coming out of the registers actually felt cool, but there was so much of it that it heated the house. My feeling is that you can compare efficiencies, but you cannot calculate payback periods because gas prices vary and weather varies. All you can do is keep track of your costs and calculate payback period retroactively. Anyway, because of abnormal weather and changes in gas prices, that unit paid me back in just over one year. I don't expect to ever match that performance again. It had some design problems and after many years, I was seeing the repairman too much. So this year I replaced it with a Bryant said to be 95.5 efficient. The biggest change I noticed is that it has air from outside the house pumped in and used for combustion. As a consequence, we don't have outside air in the house, and the air coming out of the registers is much warmer. It also has a high efficiency multi-speed blower which comes on at a lower speed during some of the furnace's idle time to circulate the warm air in the house. I haven't had it long enough to calculate how much, if any, it will save us, but the increased comfort is worth a lot. Now I'm looking at adding a heat exchanger to get some fresh air into the house
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On 01/28/2015 9:58 AM, No name wrote: ...

Unless you change something else drastically, the Btu demand to heat the house will be the same so two units of different efficiencies will produce those total Btus with the relative amounts of fuel that their relative efficiencies indicate to within a (quite) reasonable approximation.
Hence, one can do a reasonable estimation of payback period knowing past history and costs. One can't know precisely what a given winter is going to bring, granted, but that's not of real concern in getting useful estimates.
Now, if one changes the parameters by also adding/upgrading insulation or increasing the footprint of the house by adding in previously unheated/marginally-heated areas or is switching from a boiler/steam radiator to forced air, then, sure; there's enough difference as to make the computation much more difficult and certainly less accurate.
But, presuming from the question as posed that this is simply a drop-in replacement/upgrade request, I'd say he'd get a pretty good estimate simply by ratio of the proposed unit efficiency to the existing. Now, getting a reliable number for the current unit may be the biggest uncertainty altho 50-60% is probably good enough for the purpose.
I've not priced recently, but when we upgraded/replaced here about three/four years ago now, the price differential between the ~95% and the higher units started to really escalate. Same as with the SEER ratings on the AC side. The payback can get really long if one goes to the extreme. We ended up w/ a 95% Carrier and while I've not compared, the difference is notable. Of course, NG prices have peaked and dropped at least a couple times over that time period, too...
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On 1/27/2015 4:52 PM, Pico Rico wrote:

Think of it this way. On a 80% efficient furnace, 20 cents of every dollar is wasted. On a 95% efficient furnace, 5 cents of every dollar is wasted. Have your friend figure out what the savings would be by their fuel bill.
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