Would you replace a furnace that is 21 years old..

[coffeelover]

or wait until it gives out of old age and then replace it?

We are in the midwest, a furnace is used 7 to 10 months out of the year where I'm located. Much more then an air conditioner.

Our air conditioner is dead. As in we need a new one. We plan on replacing that and have the cash for it. We also have the cash to replace the furnace but husband is hesitant as he doesn't want to replace something that isn't broken.

I'm of the mindset that the furnace is old, it's lost its efficiency and why not just do them both at the same time.

We've gotten 3 quotes, we know which company we want to go with, but do we justify spending more on the furnace replacement as well?

Even though we have the cash this would dwindle our account to pretty low. We are working desperately to get our savings up and have been doing great. Yet car repairs, a window repair, new fridge due to breakdown etc etc dwindle us each and every month.

WWYD?

[Guses]

Get a quote for just a furnace replacement and compare to the combined quote. Will doing it now save you any significant install fee? How much more efficient is the new furnace? How much time until you break even? How many years will you stay in your home?

Answer these questions and you will know what I would do.

---------
Edited to add:

It MIGHT make sense to upgrade to a more efficient model but you really have to calculate it. Keep in mind that fancy furnaces with electronics and gizmos are likely to need more maintenance then a completely basic furnace.

[coffeelover]

Get a quote for just a furnace replacement and compare to the combined quote. Will doing it now save you any significant install fee? How much more efficient is the new furnace? How much time until you break even? How many years will you stay in your home?

Answer these questions and you will know what I would do.

---------
Edited to add:

It MIGHT make sense to upgrade to a more efficient model but you really have to calculate it. Keep in mind that fancy furnaces with electronics and gizmos are likely to need more maintenance then a completely basic furnace.

We would more then likely just go with the basic model furnace. We are planning on staying in our home for quite a few more years. It could be 5 or it could be 15 to 20, we aren't really sure. We love our home and our school district is awesome so no plans to move at all. Hubby and I have discussed how long we plan on staying in this home and neither of us can come up with a number.
I don't think we would save on install fee, although we would be out a huge labor fee if we had to replace the furnace in the middle of the winter.

The efficiency is much better then what we have now. Again I don't know numbers but the new furnace is 95% efficient whereas the old one is just 21 years old and has no efficiency rating from what I can find on it.
No idea how long it would be till we broke even, because we don't know the efficiency of our current furnace.

[NathanP]

Have you considered a heat pump? The previous owners of my house replaced the AC and gas furnace with a single heat pump.

Based on your statement that you use the furnace for 7+ months of the year, it might not be possible and/or cost effective.

[Pooplips]

Heat Pumps work better for mild climates. At low temeratures (<20 degrees) they lose almost all of their efficiency because they need to kick on an additional heat source, usually an electric heater, to maintain room temerature.

As far as replacing your furnace; I would do it. Furnaces have a 15-20 year life span, at 21 years you got your moneys worth. Also, in the mid 90's a base model would be an 80% efficient furnace most likely. These days 92-95% is considered base madel.

You will absolutley pay more if they come back twice. Additioanlly, older furnaces tend to be larger. So if you replace your AC now, they may have to custom build a box for your A-fram coil to make it fit with your current duct work. Then, if you change the furnace out later and the size is different, they will have to re-work the same duct work that was jsut done. Added $$.

IMO change them both save the extra money from two seperate projects and forget about it for the next 15-20 years.

[Cranky]

Yes, because I'm planning to replace my furnace and a/c next year (this year is dedicated to the kitchen remodel.)

It's probably 25 years old. It's cranking along. It's actually not that expensive to run, as natural gas is so cheap - I'm paying $41/month for heat/hot water/occasional dryer usage. I'll certainly not recoup the cost of a new furnace with energy savings.

But I hate when things conk out, especially a big expensive important item like a furnace. I would way, way, way rather replace it in the summer than on some below zero January day.

[soupcxan]

When you say furnace does that include the air handler that runs with the AC? If so, and you are already set on replacing the AC, I would definitely replace a 21 year old furnace/air handler at the same time. You will get better efficiency and comfort out of a matched AC/AH system. And I suspect it will be cheaper overall than replacing half this year and half in the next 5 years when the furnace finally dies.

[MrFrugalChicago]

Place by me offers "Free furnace if you buy an AC".

Now I think the mark up the AC to make the deal.. but I think the AC is the expensive part.

Get a quote both ways, and assume your furnace saves you 10-15% on your gas bill in the winter. Can do the math for the breakeven, but I suspect is fairly long.

That said I am in the same boat, and plan to get both.

[pdxmonkey]

Going with the basic level furnace is probably a bad financial decision as much as it sounds like you use it. I don't use mine nearly as much and the math worked out to where I went with a 97% efficient model. A lot of the cost is in install rather than the furnace itself so upgrading to a better model may be less than you think.

[lcerrito]

Fellow Midwesterner here. Our furnace was also over 20 years old, and we ended up opting to replace both the furnace and AC with a high efficiency model. The furnace kept needing repairs, and it wasn't worth the repair costs. I'm also terrified of carbon monoxide poisoning due to childhood events... so I had a little motivation there.

We were able to negotiate a 10% discount in return for paying cash instead of financing. You might try that if you are able. There is also a tax credit for efficient HVAC installs (10% of cost, up to $500), so keep that in mind.

[Jim2001]

+1 for replace them both at the same time to reduce install expense.
+1 for go with the most efficient you can afford. 
+1 for replace it now.

Waiting for it to break may leave you without it in the dead of winter when everyone else needs theirs fixed too. When it's an emergency, you likely won't have the time to shop for price.  When it's an emergency, the installer will know that and price accordingly.

[lukebuz]

Also, your A/C is the older refrigerant.  The R410A that will HAVE to replace it, will require a new A-Coil.  Getting a coil box made twice for different sized furnaces = $$.  Both at the same time, please!
Opt for the 95% single speed.  Best value, all around.  I built Condensers and Furnaces for half a decade, so I have some experience here.

[Tom Bri]

We did. 27-year-old furnace that I just got tired of looking at. It still ran, but the gas bills were high, and it was rusty and decrepit-looking, so I didn't trust it.

New one is 95% efficiency. I have not yet compared actual gas usage, but bills are way down. Part of that is the warm winter this year, and part the cheaper gas. I don't expect to actually recoup the cost of the replacement by saving gas money. However, we will be selling this place in a few years, and I think being able to list the date of the furnace is an asset.

[Tick-Tock]

Our nearly 20-year AC died in the middle of summer while we were traveling.  We decided to replace the nearly 20-year furnace at the same time.  We saved money on doing the whole thing at once and were able to shop around for the best deal (weren't desperate for the AC and went without for a few weeks).  We just really didn't want the furnace to die in the winter, especially if we were away.  The piece of mind has been worth it.

[Syonyk]

Have you considered a heat pump? The previous owners of my house replaced the AC and gas furnace with a single heat pump.

Based on your statement that you use the furnace for 7+ months of the year, it might not be possible and/or cost effective.

Midwest.  Not likely to be a viable option - it's too cold in the winter.

Even new heat pumps can't do a great job below 15-20F - the backup system comes on.

If you can get a system with the backup being a gas furnace, then that would be worth considering - cheap heat for *most* of the winter, and gas backup in the really cold months.  But most heat pumps use electrical heating coils, which are comically expensive to run.  Black comedy, mind you, but you can spend $400/mo heating with an electric furnace.

A new gas furnace is going to be a lot more efficient - you can get condensing units that get a good bit more heat out of the gas than the old units.

[NoStacheOhio]

The furnace in our last rental was like 40 years old, heat exchangers were cracked, and the attic had very little insulation. Our gas bills were $200-350 last winter (polar vortex, stretches of days with -10* real temp). Get a new furnace.

We just got a quote for a new system (furnace+AC) at our new place, and they said doing them separately would add $300-500 to the total cost, because they would then need two sets of permits, and it's easier to do everything all at once.

[FiguringItOut]

How long are planning to stay in the house?

In my last house the furnace was original to the house, which was build in mid-50's.  When we bought the house in 2008, we were told that it will need to be replaced fairly soon.

In 2013, during annual inspection by gas company, they said there was a hole in it and it needed to be either replaced for something like $5,000 or repaired for $800. 

We had no money what so ever, long story, but were living totally on the edge of the financial demise.  Anyway, I asked a friend, who used to be a technician for gas companies in the past to confirm that repair was in deed needed.  Once he confirmed, I took few months to save up for the repair and had it done.

In retrospect, it was a good decision at a time.  We ended up selling the house in 2015, so I'm glad we didn't spend the money on the new furnace.  But, with the repair, we were ok for the two more winters in the house and we were not afraid that we will lose heat in the middle of February.

I can't say if the house would've sold for more with the new furnace (and other updates that it desperately needed) as my ex was selling the house by himself after I already moved out and had nothing to do with it.  I only showed up at the closing to sign the pepares.  Didn't even know how much he sold the house for until months later when it showed up on Zillow. 

Anyhow, if you are planning to move in some not too distant future, I'd leave the furnace alone.  Even if you are planning to stay, I'd wait until it starts to need repairs and make a decision then.  Meanwhile, you can save up for a new furnace or designate some funds towards it when it becomes necessary. 

[Chris22]

Anyhow, if you are planning to move in some not too distant future, I'd leave the furnace alone.  Even if you are planning to stay, I'd wait until it starts to need repairs and make a decision then.

Disagree.  The time to do something is when you don't HAVE to, so you can shop around, not pay emergency rates, etc. 

We are semi-remodeling our house that we bought in April, and one of the first things we did was completely replace the HVAC system.  Did the whole thing for ~$5500 (1700sq ft house in Chicago burbs).  Our furnace was, at that point, about 25 years old, and we built it into our plan when we bought the house.  By the time we're done in a few months, every single substantial system in the house will have been replaced (HVAC, water heater, plumbing, lot of the electrical, appliances, etc). 

[Digital Dogma]

or wait until it gives out of old age and then replace it?

My parents went with this method and the second cold snap of the winter caused their 30 year old boiler to explode, firing pieces of metal flange and piping across the basement and causing smoke to fill the room till they cut the power (lucky someone was home at the time!). That was the weekend of New Years, they had a wood stove and were able to make it 3 days beyond that holiday to avoid triple-time pricing from the contractor they were going to use.

So, consider that you would need a backup heat source to make this method logical. Otherwise your pipes will freeze and you'll be kicking yourself in the ass for not replacing it early.

[HipGnosis]

The very first thing I'd do is have the furnace and AC serviced and inspected by a highly rated professional.
Get a quote on fixing the AC.
Get an estimate on how many years are left in the furnace.

But that said; google tells me the average life expectancy of a furnace is: 13 - 20 yrs.

[SethB]

I've been down this road twice before. It is far easier to replace something in the off season when rates are lower. The energy savings will really help to reduce the burden.

Ever tried to replace AC in the summer? It costs twice what it should. Same for a furnace in the winter.

[TheOldestYoungMan]

Dad always said, every 20 years you're going to want to look at replacing:

Roof
AC
Furnace
Dishwasher
Faucets
Wife

But mostly you'll want to replace all with new.  The wife you can use a 21 year old version if you can afford it.

[bzzzt]

I'd replace it if you have the money. It's usually cheaper to do it all at once.

That said, I'm on a 34 year old furnace and AC unit. I've had problems with both in the last few years, but I'm confident doing the work myself (Electrician + 15 years working on cars). Furnace needed a control board, pilot valve/switch, plus thermostat and the AC has blown a fuse at the disconnect. If I wasn't confident repairing things myself, I would've bought new units by now instead of blowing money on service calls.

[coffeelover]

Also, your A/C is the older refrigerant.  The R410A that will HAVE to replace it, will require a new A-Coil.  Getting a coil box made twice for different sized furnaces = $$.  Both at the same time, please!
Opt for the 95% single speed.  Best value, all around.  I built Condensers and Furnaces for half a decade, so I have some experience here.

Ahh I was just coming back here to check this thread and see what people thought about the single speed vs the 2 speed.
It seems as though the 2 speed would be more efficient but I don't know if it would be the best fit because the more parts the more likely it would be to break.
Thanks for your thoughts, they are appreciated.

[coffeelover]

The very first thing I'd do is have the furnace and AC serviced and inspected by a highly rated professional.
Get a quote on fixing the AC.
Get an estimate on how many years are left in the furnace.

But that said; google tells me the average life expectancy of a furnace is: 13 - 20 yrs.

Everything has been serviced last year. AC is done though it can't be fixed.
Furnace is running in good condition. No issues that can be found. No one will tell me how long the furnace has, they say, "could go tmr, or it could last 10 more years."

[coffeelover]

Dad always said, every 20 years you're going to want to look at replacing:

Roof
AC
Furnace
Dishwasher
Faucets
Wife

But mostly you'll want to replace all with new.  The wife you can use a 21 year old version if you can afford it.

I am the wife, I am the 2nd version but older model. I think I'm better lasting, made quite well, built like a farmer, can cook anything my hubby desires and I know how to fix stuff, plus I'm a good communicator, an awesome wife and I know what my husband is thinking just by looking at his face.
My husband is my first version though, I don't think I want to invest in a different model. I've grown used to the heat he gives off.

[SethB]

Ahh I was just coming back here to check this thread and see what people thought about the single speed vs the 2 speed.
It seems as though the 2 speed would be more efficient but I don't know if it would be the best fit because the more parts the more likely it would be to break.
Thanks for your thoughts, they are appreciated.

I don't know about two speed systems but in commercial application with variable speed drives the equipment lasts longer because starting is smoother.

[Syonyk]

Ever tried to replace AC in the summer? It costs twice what it should. Same for a furnace in the winter.

Yeah.  The "Huh.  It's -10F and snowing with winds 30 gusting 50" labor adjustment isn't cheap.  Neither is the "It's 105F and somehow about 105% humid" adjustment.

[music lover]

How can anyone give sound advice to replacing a furnace when no information was provided as to how much your heating costs are?

Going from 80% efficient to 95% only saves $150 on $1000 in heating costs. If a new furnace costs $5000, then the payback is 33 years. But, a 5% return on that $5000 gains your $250 a year...$100 more than what you would save in heating.

[Syonyk]

You're way high on costs, though if you live in an expensive area with a big house, $5k might be doable.

http://www.homeadvisor.com/cost/heating-and-cooling/install-a-furnace/

Replacing a furnace for pure cost savings probably isn't worth it - spend the money on insulation instead.

But replacing a furnace preemptively before it fails in the dead of winter is going to save you a bit over an emergency call and trying to keep your pipes from freezing.

[Chris22]

How can anyone give sound advice to replacing a furnace when no information was provided as to how much your heating costs are?

Going from 80% efficient to 95% only saves $150 on $1000 in heating costs. If a new furnace costs $5000, then the payback is 33 years. But, a 5% return on that $5000 gains your $250 a year...$100 more than what you would save in heating.

Not necessarily a reason to do it, but I got some pretty substantial cash, like $600?, from my electric and/or gas co for replacing my ancient HVAC system with a new one.  But really, the increased efficiency/cheaper usage costs are just icing, what I was really buying was reliability that I was concerned wouldn't be present in my 20+ y/o system.

[pdxmonkey]

How can anyone give sound advice to replacing a furnace when no information was provided as to how much your heating costs are?

Going from 80% efficient to 95% only saves $150 on $1000 in heating costs. If a new furnace costs $5000, then the payback is 33 years. But, a 5% return on that $5000 gains your $250 a year...$100 more than what you would save in heating.

Your math is off by a few percentage points of savings. Lets say you need 800 therms to heat your house with an 80% unit and each therm is $1. This means you need to buy 1000 therms and and convert 80% of them to heat thus spend %1000. With a 95% efficient unit you need to buy 842.1...therms and convert 95% of them to heat. You save... almost $158! or slightly over 5% greater savings than $150.

Now all we need is for someone to build a calculator like this one, but for Mustachians.: http://www.energytools.com/calc/EnerEcon.html
This calculator has no ability to set loan interest rate to 0%. It also doesn't seem to let you adjust expected returns on the alternative investment.

[Jon Bon]

I'm surprised by the responses.

If you sub out "furnace" and replace with "car" I feel you would get very different answers.

Honest question: is the saying replace the furnace every 20 years about the same as change your oil every 3000 miles. Is it just outdated advice with the advent of modern  manufacturing?

[aneel]

Yes, and then sell the old furnace on Craigslist (what we did) to help off set the upfront cost.

[coffeelover]

Yes, and then sell the old furnace on Craigslist (what we did) to help off set the upfront cost.

Sell the old furnace, now I'm intrigued?

How much did you get for it, how old was your unit?
Of course the companies offer to take it away for free and then I'm sure they wills scrap it and get money for it.

I would rather make money on my old stuff then just give it away.

[Chris22]

Yes, and then sell the old furnace on Craigslist (what we did) to help off set the upfront cost.

I asked my furnace guy about this when I had mine replaced, and he told me there is zero resale value in the thing.  He said he scraps them, and gets some minimal ($25? $50?) money for his effort.  Maybe he lied, or maybe he's just being dumb, but I have to think if there was any significant resale market on a furnace he'd be in the game (he works for an HVAC company by day and freelance installs equipment on the side, so he's hustling).  A glance at my local c-list suggests there are a fair number on there for ~$125 or so.  No idea how fast they sell.  I personally didn't want to take the risk for a $125 gain versus having a large bulky thing to dispose of if I couldn't move it.  This was at the same time I was trying to sell a garage full of decent quality great condition furniture, the vast majority of I ended up donating because no one wanted it, so I maybe was a little less ambitious.

[SethB]

I'm surprised by the responses.

If you sub out "furnace" and replace with "car" I feel you would get very different answers.

Honest question: is the saying replace the furnace every 20 years about the same as change your oil every 3000 miles. Is it just outdated advice with the advent of modern  manufacturing?

No.

For one thing, there is a huge difference between the the repair:replace ratio. The last new AC that we replaced cost $4,000 to replace and $1,000 to fix every year. The furnace was $7,000 to replace and $500 to fix. The AC went from 10 to 26.1 SEER. The furnace went from 50% AFUE to 97%.

In a car, you would need to be spending $2,000/yr on unscheduled maintenance to hit these same numbers.

Similarly, the difference in operating costs is huge. We are talking about 50% reductions in gas spending. 70% reductions in air conditioning costs. And because the new unit that we replaced the AC with was a heat pump it can provide heat to the living room, which allowed us to remove the fireplace insert for even more gas savings.

Best part? We ended up renting the place out and haven't gotten a phone call on either (after replacement) in about eight years. Which is good because the house is over 300 miles from home.

[Chris22]

I'm surprised by the responses.

If you sub out "furnace" and replace with "car" I feel you would get very different answers.

Honest question: is the saying replace the furnace every 20 years about the same as change your oil every 3000 miles. Is it just outdated advice with the advent of modern  manufacturing?

No.

For one thing, there is a huge difference between the the repair:replace ratio. The last new AC that we replaced cost $4,000 to replace and $1,000 to fix every year. The furnace was $7,000 to replace and $500 to fix. The AC went from 10 to 26.1 SEER. The furnace went from 50% AFUE to 97%.

In a car, you would need to be spending $2,000/yr on unscheduled maintenance to hit these same numbers.

Similarly, the difference in operating costs is huge. We are talking about 50% reductions in gas spending. 70% reductions in air conditioning costs. And because the new unit that we replaced the AC with was a heat pump it can provide heat to the living room, which allowed us to remove the fireplace insert for even more gas savings.

Best part? We ended up renting the place out and haven't gotten a phone call on either (after replacement) in about eight years. Which is good because the house is over 300 miles from home.

Plus, in many places, if your furnace goes out in the winter, it can cost you FAR more A) to fix, and B) if you don't fix it (pipes freeze).  It's not like a car where you can make realistic alternative arrangements for a couple weeks (or indefinitely if that's your thing).  A burst pipe and water damage can make a $5k furnace replacement seem like peanuts.

[greaper007]

I have a furnace from 93 and I think it's 72% efficient.   We keep our house at 56 during the day and 62 at night, during January and February my bills generally don't top $140 (combined electric and gas) with about $70 of that gas.   So I might spend about $350-$400 on gas for the furnace each year.   Going to  ~90% efficiency would only save me about $80 for the year.    I'd never recoup the extra cost for a more efficient furnace, I'm guessing that you wouldn't either.

Here's a tip for dealing with mid-winter breakdowns.    My furnace broke on the coldest day of the year two years ago.   We woke up to a house that was about 45F.     I'd never fixed a furnace before, but I'm willing to take a look at anything.    So I took off the front cover and started looking for problems.    I quickly discovered that it was going through the whole ignition cycle, but failing to light.    I noticed there was a piece that looked like an ignitor that wasn't heating up.   Did a quick google search and found that it was indeed an ignitor.    I could buy a new one off of prime for about $45.    Considering that the outside temperature was about 15f that wasn't going to work.   So a quick search found that there was a furnace repair store in S Denver that sold to the public.    They had the part in stock for about $65 I drove down and bought two, and a few other parts just in case that wasn't the source of the problem.    I plugged it in and it was fixed.    Took all of 5 mins.   

I'd suggest keeping an inventory of parts for your furnace and figuring out how to fix it now, so that if it does breakdown during the winter you'll be good to go.    Off the top of my head I'd say the ignitor, the flame sensor and maybe even a new control board.    You could buy all of those for less than about $350 on the internet.    Otherwise, furnaces are pretty robust, simple pieces of metal that can go for a very long time.   They're much simpler to fix than a car (which I've also had to fix in the middle of a cold night).    At my old house in CT I had an oil furnace made by Chrysler that dated to 1954, we never had a problem with it.

[CowboyAndIndian]

I have a furnace from 93 and I think it's 72% efficient.   We keep our house at 56 during the day and 62 at night, during January and February my bills generally don't top $140 (combined electric and gas) with about $70 of that gas.   So I might spend about $350-$400 on gas for the furnace each year.   Going to  ~90% efficiency would only save me about $80 for the year.    I'd never recoup the extra cost for a more efficient furnace, I'm guessing that you wouldn't either.

+1

My furnace is from 1986. I'm going to run it as long as it runs.

My utility company offers a service plan (approx $10/month) which have added for the furnace. When the solenoid failed or when the fan was making noises, they fixed it.

[aneel]

Our situation was a bit different as we had a boiler, not furnace, and it was relatively new - 7 years old.  We were switching from oil to gas at the time.  Our contractor also told us that he wouldn't take it and that it wasn't worth anything used.

We sold it for $500!

[Jon Bon]

I'm surprised by the responses.

If you sub out "furnace" and replace with "car" I feel you would get very different answers.

Honest question: is the saying replace the furnace every 20 years about the same as change your oil every 3000 miles. Is it just outdated advice with the advent of modern  manufacturing?

No.

For one thing, there is a huge difference between the the repair:replace ratio. The last new AC that we replaced cost $4,000 to replace and $1,000 to fix every year. The furnace was $7,000 to replace and $500 to fix. The AC went from 10 to 26.1 SEER. The furnace went from 50% AFUE to 97%.

In a car, you would need to be spending $2,000/yr on unscheduled maintenance to hit these same numbers.

Similarly, the difference in operating costs is huge. We are talking about 50% reductions in gas spending. 70% reductions in air conditioning costs. And because the new unit that we replaced the AC with was a heat pump it can provide heat to the living room, which allowed us to remove the fireplace insert for even more gas savings.

Best part? We ended up renting the place out and haven't gotten a phone call on either (after replacement) in about eight years. Which is good because the house is over 300 miles from home.

Is the OP having repair issues or is it just old?

I totally get it when it comes to repair, 1000 repair or 2000 new furnace is a no brainier to me.

I don't agree with folks saying it's gonna die,  the pipes are going to freeze and damage your home.

It's much more likely your power will go out in winter time and we all cope with that Dont we? The bad weather price preimim might be a real thing but lack of heat being a doomsday scenario is a bit overblown.

[Guses]

he bad weather price preimim might be a real thing but lack of heat being a doomsday scenario is a bit overblown.

+1

Especially given that the doomsday scenario can be mitigated by a few 10$ electric heaters found in pretty much any store.

If efficiency gains are not enough to break even in a reasonable amount of time, it makes no sense to upgrade "just in case it breaks".

[coffeelover]

I'm surprised by the responses.

If you sub out "furnace" and replace with "car" I feel you would get very different answers.

Honest question: is the saying replace the furnace every 20 years about the same as change your oil every 3000 miles. Is it just outdated advice with the advent of modern  manufacturing?

No.

For one thing, there is a huge difference between the the repair:replace ratio. The last new AC that we replaced cost $4,000 to replace and $1,000 to fix every year. The furnace was $7,000 to replace and $500 to fix. The AC went from 10 to 26.1 SEER. The furnace went from 50% AFUE to 97%.

In a car, you would need to be spending $2,000/yr on unscheduled maintenance to hit these same numbers.

Similarly, the difference in operating costs is huge. We are talking about 50% reductions in gas spending. 70% reductions in air conditioning costs. And because the new unit that we replaced the AC with was a heat pump it can provide heat to the living room, which allowed us to remove the fireplace insert for even more gas savings.

Best part? We ended up renting the place out and haven't gotten a phone call on either (after replacement) in about eight years. Which is good because the house is over 300 miles from home.

Is the OP having repair issues or is it just old?

I totally get it when it comes to repair, 1000 repair or 2000 new furnace is a no brainier to me.

I don't agree with folks saying it's gonna die,  the pipes are going to freeze and damage your home.

It's much more likely your power will go out in winter time and we all cope with that Dont we? The bad weather price preimim might be a real thing but lack of heat being a doomsday scenario is a bit overblown.

Repairs were made to the furnace right before we bought the home last year. We have had 0 issues thus far with furnace. So basically furnace is old but has had issues in the past.
The air conditioner is dead, not repairable and needs to be replaced. Which we plan on doing by mid May.

[powskier]

Replace furnace in summer. Replace before it is broken. This summer, next summer, or the one after that part is risk management.....up to you.
If you do not it will break on the coldest day of the year, at the same time as many others. Maybe Murphy's law but more likely just time of max output will max things out.

[coffeelover]

Replace furnace in summer. Replace before it is broken. This summer, next summer, or the one after that part is risk management.....up to you.
If you do not it will break on the coldest day of the year, at the same time as many others. Maybe Murphy's law but more likely just time of max output will max things out.

This is how things usually work for us. Things break right in the moment of need.

Which is why I would feel safer replacing the furnace now. Yes it would be nice to have lower heating costs. Although I do not expect that to happen. I don't think 'we will break even.' for quite some time.

[Frugal Lizard]

I wouldn't replace the 21 year old furnace just to get a savings on the air conditioning unless the saving was really substantial and there was something wrong with the existing furnace.
In the three houses I have owned I have replaced one furnace.  All had old or very old not so efficient models.  The no bells and whistles ones did what they needed to do - turn on and heat up.
I replaced the monster huge, extremely old furnace (33years) that was sitting in the middle of the basement room blocking a very large window that could have provided daylight to a huge room.  The HVAC service tech I had evaluate it shortly after we moved in said it was running ok but buy brand new CO detectors.  It had been rebuilt because there had been problems but he wouldn't have that model in his house.  He didn't sell furnaces, just repaired them. It ran really really loud and woke the kids up every morning when it turned up the heat from the overnight temperature.  All parts of the basement were not warm and we have a walkout and lots of usable space down there.
I replaced it with a high efficiency variable speed quiet model that the fellows were able to tuck into a corner of the basement beside the chimney.  The venting of the old furnace was incorrectly installed and the ducting was not installed in the most efficient way either.  I did it in April with getting four quotes. It was fairly complicated because of moving the location and needing to make sure the rest of the basement was going to be warm so I needed some HVAC expertise.

[qval]

As far as replacing your furnace; I would do it. Furnaces have a 15-20 year life span, at 21 years you got your moneys worth. Also, in the mid 90's a base model would be an 80% efficient furnace most likely. These days 92-95% is considered base madel.

You will absolutley pay more if they come back twice. Additioanlly, older furnaces tend to be larger. So if you replace your AC now, they may have to custom build a box for your A-fram coil to make it fit with your current duct work. Then, if you change the furnace out later and the size is different, they will have to re-work the same duct work that was jsut done. Added $$.

OP, the duct sizing question is very important. Also, be sure they replace the furnace with a smaller one (unless your furnace never turns off when it's 0F or 10F or whatever your design temp is).  A furnace is more efficient if it doesn't turn on and off all the time (lower cycle count), and it'll last longer.

Back to the duct question, it seems like new, high efficiency furnaces are designed to have lower back pressure, and suction side pressure drop (compared to 20 years ago). This means you'll want a complete duct redesign anyway (what's the r-value on they ducts, r-8? or r-13?)
which will add a lot to the cost of your HVAC project.

I'm not positive you want to replace the furnace now, but consider going with a smaller BTU output that what you have. Make sure you look at BTU output for a size comparison, not BTU input, because higher efficiency means a 76k BTU input furnace @96% efficiency is now bigger than an old 100k BTU input furnace that's 72% efficient.


Aside: I'm dealing with this pressure drop issue myself right now. New furnaces are rated for a 35-65F temp rise, while old furnaces could cope with 100F+ temp rises ( that's the change in temp from the return to the delivered hot air). But that means you either need to flow a lot more air, or put in a lot less heat. My furnace was way off at 90F temp rise, where the spec says 35-60F. I ended up using the highest fan speed, and also dropping the gas regulator pressure from 3 inches water column to about 2 inches.

This made my furnace a 48k BTU heater, from a 70k BTU heater. The house is still plenty warm, though it warms up a bit slower after we get back from a long trip, and left the thermostat at 45F. I live in Boise, ID, which doesn't get as cold as the midwest, but I'm not in SoCal either. So if you have a 120k BTU input furnace now, get one with 90k input or 70k input. It'll only be 10-20% smaller, but it'll last longer, be cheaper to buy and operate, and keep your house just as warm.

[GuitarStv]

Dad always said, every 20 years you're going to want to look at replacing:

Roof
AC
Furnace
Dishwasher
Faucets
Wife

But mostly you'll want to replace all with new.  The wife you can use a 21 year old version if you can afford it.

I am the wife, I am the 2nd version but older model. I think I'm better lasting, made quite well, built like a farmer, can cook anything my hubby desires and I know how to fix stuff, plus I'm a good communicator, an awesome wife and I know what my husband is thinking just by looking at his face.
My husband is my first version though, I don't think I want to invest in a different model. I've grown used to the heat he gives off.

In case you want a change, it's always possible to increase the heat he gives off by wearing less clothing around the house.  Strange but true.

[scottish]

I'm surprised nobody has raised the issue of carbon monoxide from a leaky, corroded, heat exchanger.    Does anyone see this as a potential reason for changing your furnace?   Or are they all boilers instead of forced air?