This discussion was created from comments split from: 22-year heater, repair or replace?.
Revisiting this older thread…new furnace needed! We have an 80% unit about 20 years old. One contractor explained that even if we wanted to switch to a 95% high efficiency unit, given the age of our house, it won’t perform much better than the older units. (House is from the 50’s with adequate attic insulation, but minimum if any wall insulation, and older windows). Makes sense, so wondering if we should simply replace with a new 80% unit. It is about half the cost!
First of all, I’m no expert and certainly don’t know enough to give anyone advice. However, the logic seems backwards to me. If a house doesn’t have good insulation, it seems that the furnace would need to run more and you would benefit from a higher efficiency unit. If I go the the extreme and say that there is such a thing as a super insulated house that loses and gains zero heat, the furnace would turn on once and never be used again. Why would I pay more for a one time use furnace that used a little less gas?
Look carefully at the energy rebates out there. They may pay for much of the additional cost of the more efficient unit and you get to reap the savings (even if small) of that extra efficiency.
I have a house similar to what you describe, and I would go for the high efficiency unit, what the guy said made no sense to me. Whatever the level of insulation, the furnace will fire when the thermostat reaches its set point, and that has nothing to do with the efficiency of the furnace. So let’s say it is 40 degrees outside, and your thermostat is at 68, and let’s say to maintain that thermostat reaches its set point (in this case, likely 67 or 66 degrees, depending on the thermostat), it will fire 10 times that hour. The more efficient unit will likely take less time to heat the house up and more importantly will do it using less fuel. Whether you have a thermally sealed house or not, that doesn’t change, a more efficient furnace will use less fuel.
What I suspect he is arguing is ‘you will never get your money back’, that if you pay let’s say 3k more for a 95% efficient unit, the fuel savings will not pay for it…if the high efficiency unit saves you 300 a year, then it would take 10 years to ‘pay back’, which given a typical furnace will last 20-25 years, means you would be in the black…I would look at your current heat bill for the year, figure out the savings, then see how it plays out (assume the 15%, or to be conservative, use 10%) and see how long it would take to pay back.
Me, i would go for the higher efficiency unit, when I get around to replacing our second unit (which is around 85%) I likely would go for a high efficiency unit. Among other things, I am convinced that the high efficiency units tend to run better with less problems (just my experience).
One thing also to count in is the brand and the quality. I have heard they “are all the same”, and while the basics of a furnace (a firing chamber, a heat exchanger and a fan to circulate the air over the heat exchanger) are the same, I have gotten to know a number of the guys who work on furnaces and boilers, and they say there is a difference. Companies like Trane, American Standard (same company makes both), Carrier and Bryant tend to be more reliable, some of the no name brands the Home Depot and the like carry are not so great in their experience, so if it came down to a high efficiency in one of the no name brands verus a less efficient one with one of the better brands, I might go that way if my budget only allowed that.
We have three high efficiency units running in this house (one on each level). The bills are substantially lower in this house than they were in the previous house without high efficiency units (two regular gas furnaces).
This house is newer and better insulated, but we live in a moderate climate so it’s not a huge factor in the wintertime in terms of keeping either house warm.
Our home is 20 years old and we went for the high efficiency unit when we replaced the system. We also added R50 insulation in the attic. Rebates paid for 1/3 the cost and the balance is being paid over 10 years at no interest. We just received a letter from the utility letting us know that compared to similar homes in the area we used almost 50% less terms than similar homes.
Best of all is the quality of the heating and cooling. Our home is just more comfortable.
My house is 100+ years and the outside wall insulation is poor. What I think some need to factor is that, with even a 95% unit, the heat from that wonderfully efficient producer is going to go straight out the walls and windows.
My furnace is 80% (oil/steam,) is over 30 years old. When it comes on, downstairs rooms heat beautifully. The temp rises, it shuts off…and 15 minutes later, it’s cold(er) again. Like many who live in old homes, we live with this.
My oil techs are mostly old guys with decades of experience. They say, don’t lose the furnace yet. Not at 80%. My plumber says the same. What we may do is add a supplemental hot water tank, to make bath water hotter.
We replaced some parts of the attic/roof insulation this summer, where it failed. We’ll see if that helps the 2nd floor retain heat this winter.
@lookingforward I’m guessing since you have oil as a heat source that you live in a cold winter area of the US?
@kjofkw what part of the country do you live in? I can see where what looking is saying makes sense if you live in a super cold area with little insulation, and what I have could make sense if you live in a moderate winter climate.
My house is only 60 years old and I replaced my oil/hot water furnace about 10 years ago with the most efficient boiler made ( Buderus.) Our old furnace kept breaking and we had to have it serviced at least a few times every year. I have replaced all the windows in my house and insulation was stuffed down under them when they were put in. The only room with excellent insulation is the family room addition we put on in 2008. The rest of the house has that crappy vermiculite.
My usage went down dramatically with the new furnace. I kept all my oil delivery bills so was able to compare the oil usage from before and after. We also put in a second zone in the basement which helped, too, but there was only one small bedroom down there that had heat before but now the whole basement does.
Yes, we’re in New England and most winters are a bear. Keeping the temp set at 68 would be a dream. Many old homes here and we joke about how low we set the thermostat. Many of us turn on a space heater, just as needed, when we’re in that room.
We couldn’t insulate the outside walls previously, due to the sorts of wiring running up them. We’ll need to check how the new advanced materials might work.
Basement is fine, though. The furnace radiates some nice heat there.
We are in a 92 yo brick 1800 sq. ft. home in the Chicago area. When we first moved in, about 17 years ago, we began to replace the windows, one section of the house at a time. It helped, a bit. There is no insulation in the walls. We did have more insulation blown into the attic, and that seemed to help.
Our old furnace did give out a few years ago, and we replaced it with a high efficiency (92%) Rheem gas furnace. I don’t recall the sticker shock being that bad.
The biggest improvement to feeling comfortable inside this old house during the depths of winter is the Jotul wood burning fireplace insert we installed about 10 years ago. We can pack it with wood, get a really good fire going, turn on the electric fan, and the coldest room in the house is suddenly TOASTY.
The upstairs of the house gets quite warm (heat rising) when the Jotul is cranking, and of course, the furnace is not kicking on during those times. The fan on the wood stove does cause the electricity bill to rise.
@lookingforward Laughing at the “how low we set the thermostat”…yes, we totally do that with our friends in the area. I can still hear my mother, “Put on a sweater!” 
Surprising how those gas fireplace units can heat up a room, too. We may go for one, if we can figure the flue.
@Midwest67 we all play the game (except families with young kids.) “Mine’s at 64.” “Yeah, well mine’s 62.” “Hoho, mine’s at 60.” Last few winters were ok, by NE standards, and I went below that.
No one should think we like this, haha. I daydream about a newer, smaller, energy-efficient home.
IME, the ultra-high efficiency (95%+) units break down more often and are significantly more expensive to repair and maintain. So factor that into the price comparisons as well.
Keep in mind those are theoretical efficiencies, in actual use YMMV as they say. Depending on the thermal characteristics of your house, the local climate, the features of your unit, and how accurately sized the the unit is, the actual efficiency may vary quite a bit, and it is possible a 95% unit may not actually be 10% better than an 85% unit. Probably the single biggest factor is sizing it correctly, because that controls how often it will cycle. Too-frequent cycling is inefficient and will wear it out faster, leading to higher maintenance or a shorter lifespan.
I put an 85% Buderus in my house, with an outside air temperature monitor and storage tank for hot water. It was more than the 80% Burnham and WM, but the extra cost was almost entirely made up from rebates from the gas company. It didn’t seem worth it to go to 95%.
Our thermostat is set at 59 during the night and daytime when everyone is gone, and 63 when when we are home and awake (though I admit sometimes I bump it up to 65).
I keep my thermostat at 71 when we are at home. I refuse to be cold in my own house, I don’t care what the heating bill is. So what if my kids get a slightly smaller inheritance, at least I was warm.
- Amazing number that never crosses my thoughts here in winter. At the gym, maybe. lol. Ok, unless we'e entertaining at dinner time.
I will not be cold in my own house. Life’s too short.
I don’t care if it costs me an extra $100/month. 
Same here. I’m always cold. We keep our heat at 68 when we are here, but if I get chilly, I’ll bump it up to 71 or 72. And yes…I dress warmly. Rig now I’m wearing a turtleneck and a fleece top over it. I got chilly so I bumped the heat up to 71…the. Turned it back down to 68. It took the chill out.
I also won’t be cold in my own house!
Go for it with the high efficiency furnace- for comfort. A two stage blower will have a high speed when the temperature needs to change a lot (such as temperature extremes or changing the thermostat settings a lot- say after returning from vacation) and a low speed most of the time. This keeps you more comfortable by having more frequent slow “gusts” of air instead less frequent “blasts” of hot/cold (same principle for running an air conditioner) air. Feels better to have a little bit almost constantly than the single stage.
Another thing to replace (unless you have recently) is the thermostat. It is so nice to set different temperatures for different times of day. Honeywell makes several models with different price ranges. From what I’m hearing the Nest may not be as reliable, plus I dislike its display format and don’t need the fancy wifi et al whistles and bells.