Gas Furnace - To Fix or Replace

[Nifty]

We're in a new place that has a gas furnace that hasn't been started up in about 3 years. Back then it worked fine, but it's got some issues now.

We have a repair guy come over to look at it and he said, "Oh wow, this is an old unit and it's only about 80% efficiency. Instead of putting money into fixing this old one, we can put in a new unit that is about 95% efficient!"

So, I thought I'd do some math and present it here. Please review and let me know what you think:

Facts:
We don't use our furnace very much. We're in a pretty temperate climate and I'd guess we'd only use it sparingly every day for about 2-3 months.
I'd say the average gas bill for someone around here that uses gas to heat their home is $50 - $100 a month during the winter (mostly guessing).
It would probably cost $250 - $500 to fix our current old furnace
It would probably cost about $4,000 to get a new unit and have it installed

So, here's my quick calculation:

I'm going to error on the side of being aggressive with the costs and savings to best case scenario for a new furnace.

Let's say our bill is $100 a month for 4 months.
Let's also assume a new furnace lets us go from 80% efficiency to 100% (impossible, but I like round numbers for quick / easy math)

So, a 20% increase in efficiency should equate to 20% reduction in monthly costs. $20 savings per month for 4 months a year is $80 per year saved.

A new furnace is $4,000, which means my break even on just gas consumption price is about 50 years!

Of course, we'd need to factor in the costs of maintaining an old furnace and the fact that the old furnace will eventually need to be replaced (as would a new one eventually), but the numbers are so grossly leaning toward fixing the current one that I just don't see any reason to even think about getting a new furnace.

What do you think?

 

[FarmerJamie]

Any tax breaks/rebates available for putting in the more energy efficient model?

How long do intend to remain in the house? (thinking sale-ability down the road)

A family member replaced a furnace with a questionable ROI, but she had central air put in at the same time. She's pleased as punch

 

[Nifty]

Great questions!

I haven't looked into rebates, but if they are significant, that could make a difference.

Stay in the house: We have no idea. Anywhere from 3 - 30 years.

Our current system is setup to accept A/C, but our summers are so mild that we usually do just fine without it. We do have a window "whole house fan" and will be putting in a real big whole house fan, and those make all the difference in the summer.

UPDATE:
The service guy just came by and swapped out the control unit ($140) and charged us $110 to install it, test the system, do some cleanup, etc. So for $250 we're back in heat business!!!

 

[FarmerChick]

Good deal. I would say with the amt. of use you get from the furnace, which is low usage as you said, I would have said FiX IT and wait til that sucker dies then spend the bigger bucks. Sounds like you are back up and in business very cheaply

 

[~gd]

Great questions!

I haven't looked into rebates, but if they are significant, that could make a difference.

Stay in the house: We have no idea. Anywhere from 3 - 30 years.

Our current system is setup to accept A/C, but our summers are so mild that we usually do just fine without it. We do have a window "whole house fan" and will be putting in a real big whole house fan, and those make all the difference in the summer.

UPDATE:
The service guy just came by and swapped out the control unit ($140) and charged us $110 to install it, test the system, do some cleanup, etc. So for $250 we're back in heat business!!!

Duh, I was going to ask about other uses for gas like water heater, laundry dryer, range etc. Many are suprised at the amoint of gas that is used for other puproses rather then heating, heck I get along on two gas heaters vented through the wall. One other hint open those A/C ducts during the summer with your whole house fan to get better air distribution, and it is a heck of a lot quieter than opening windows~gd

 

[Britesea]

How big is your house? When your furnace finally dies the True Death, do some research on how big a furnace you really need. Sometimes the service company will try to sell you more than you need.

Our house is 850 square feet. We are presently using an ancient dinosaur of a furnace (I'm guessing 50 years old or more). The last time I had to call someone in, he was able to fix it, but he warned me that some of the parts are no longer available, so we are on borrowed time. He also offered us a $4K heater.
I was at the local hardware store last week however, and ran across a gas/propane wall mounted heater that is rated for 1000 square feet (whole house for us, in other words). The cost? $250 dollars. Even if we have a professional install it, we are looking at Much Less than the $4000 quoted by the service guy 5 years ago. I still have to do some more research into it, but right now this is looking pretty good to me. Even if it's efficiency is less than the expensive furnace, I suspect it will be better than our dinosaur (and our typical winter gas usage is about $95 a month).

 

[Nifty]

Here's my report on gas usage / cost for the past month. Can you tell when my furnace was turned on?

We turned the furnace on the 14th.

Our daily price was about $1 - $2 a day before using the furnace and is now $3 - $4 a day.

So, heating our house is about $2 a day extra. If we turn on the furnace 7 days a week, that's a max of about $60 a month.

Honestly, with how much my wife and I HATE cold and how much we're LOVING having central heat, we'd easily pay twice that amount!

 

[~gd]

Here's my report on gas usage / cost for the past month. Can you tell when my furnace was turned on?
http://sufficientself.com/forum/uploads/2_gas-usage.png

We turned the furnace on the 14th.

Our daily price was about $1 - $2 a day before using the furnace and is now $3 - $4 a day.

So, heating our house is about $2 a day extra. If we turn on the furnace 7 days a week, that's a max of about $60 a month.

Honestly, with how much my wife and I HATE cold and how much we're LOVING having central heat, we'd easily pay twice that amount!

Prices change Hourly? That is a smart gas meter! I am on propane so the only info I get is when they fill the tank and I am on a budget plan to so my payments stay the same. I track by my electric bill and it follows the heating degree days pretty well [those fans that circulate the heat use a lot of power] I like cool-cold temps for sleeping so I usually turn off about a hour before I go to bed.

 

[Nifty]

A quick update: We made it through the 2013 - 2014 Winter just fine. When we fired it back up two months ago (after not using it for about 8 months) it fired up perfectly.

It does seem to be making some odd noises as it starts up and shuts down, but we have no idea if that's just how it's always been. What I do know is that it keeps us nice and warm, and the timer settings really help us save gas while also making the house nice and warm right before we wake up in the morning!

 

[Denim Deb]

Since it was cold in here this morning, that sounds nice.