[Randy]

The furnace in my home is the original, circa 1977, that came with the house. It works fine. What can I gain with a modern gas, forced air furnace? It would be nice to have a quieter blower, but even a new furnace has to send the air through the house. Any furnace experts here?

[Devil Doc]

I'm no expert, but you'll certainly gain efficiency.

Doc

[JerryM]

I'm no expert, but you'll certainly gain efficiency.

Doc

Along with designed obsolescence.

Have you done the math, Randy? Get a few bids from the most reputable General Contractors you can find. Ask them about utility company or state/local rebates. Ask them about local permits and permit fees. Talk to local utilities yourself, too. Determine your 'payback time', and make a decision from there.

Also, don't forget the designed obsolescence part. Make sure the most reputable General Contractors you can find list Warranty terms in no-nonsense language. Make sure the warranty covers the furnace flue pipe, and the roof penetration surrounding the flue. Lastly, make sure your Homeowner's insurance company is involved, including a new Policy that lists coverage for the new furnace. Pay close attention to any exclusions, and negotiate Coverage pricing that insures the Exclusions that you find too risky. Don't forget to use this new Policy price within your payback time calculations.

Have fun,

Jerry

[Devil Doc]

You have a penchant for the obvious. I don't think there's anything made today that isn't designed for obsolescence, or to simply breakdown in X amount of time.

Doc

[JerryM]

You have a penchant for the obvious. I don't think there's anything made today that isn't designed for obsolescence, or to simply breakdown in X amount of time.

Doc

You're kidding, right? 

[JLM]

A 1977 furnace is probably on it's last legs (average life of a furnace is 30 years).  Has it been routinely maintained? 

How long to you plan on staying there?  (How much do you want to invest?)  How well insulated is your house?  How big/stretched out is the house?  If you live in a mild climate you could do with an air-to-air heat pump.  If you routinely only use portions of the house you could install individual room heat pumps (very efficient).  If well insulated, live in cold climate, and plan on staying for the long haul you could consider an extremely efficient air-to-ground heat pump.  Another option for well insulated homes is to use on-demand water heaters for domestic hot water and space heating.  But the standard solution is some variation of a high efficiency furnace, which should reduce energy use by a 1/3rd.

Is the existing ductwork exposed?  (Fiberglass ductwork makes it harder for the fan to push air through but are very quiet, but only practical if you have easy access to the ductwork.)

[ctviggen]

In our previous house, we had an old oil furnace.  We converted it to a new Buderus furnace with integrated water heater, and saved about a tank of oil (200 gallons or so) or so per year. Buderus is a German (or at least European) company known for good equipment.  Depending on oil prices, that could be $600+/year.  It wasn't cheap to buy and install, though.  However, the furnace needed replacing anyway.

[Wayner]

I put in a new 96% efficient furnace 2 years ago. It needed a horizontal PVC chimney, but the water heater still used the vertical chimney so that wasn't a big deal. I also got a nice rebate from the local utilities.

Here is the kicker, my largest utilities bill for last January (gas and electric combined), with the thermostat set at 72° was $150, heating just shy of 3,000 sq. feet. Hows that? I live in Minnesota.

Wayner

[PRELUDE]

Before you think about saving or what you should buy, make sure to hire the right contractor to get job done.
Not only your 1977 furnace is not efficient anymore or loud, it is most likely to be over sized as well. You think it is working good right now because you most likely did not try  the most comfortable one yet. We always want to think the bigger is better and specially when it comes down to furnace and people are afraid to stay cold, things might go very long.
If your contractor wants to replace your furnace with the match BTU rating as the old one or refuse to do the manual J, you should tell him have nice day sir.
Manual J is the term used for load calculation and it depends on many factors like where you live, size of your house, type of insulation used in the wall etc...
If the contractor refuses to give you a written manual J report, then do not hire him.
Even if you buy a highest efficient furnace and it is not sized right, you most likely not going to save at all. If your furnace is too big for your house it will short-cycling and reduce  the efficiency and life of the furnace itself.
If you looking for the best comfort and efficient, then you have to forget about single stage and look for a two stage furnace.
         Two stage furnaces, also known as two speed furnaces, operate much more efficiently than a single stage furnace. The first stage of this type of furnace operates the majority of the time in most climates, and runs at about 65% of the furnace's full capacity. When the temperature outside becomes extremely cold and the first stage is not sufficient enough to heat your home, the second stage kicks on to provide the additional heat requirements. A 2 stage furnace provides the right amount of heat to efficiently satisfy your home and family's needs.

In addition, a 2 stage furnace is much quieter since it doesn't operate at 100% capacity every time it runs, and creates less carbon dioxide emissions for the environment.

[macrojack]

Since your furnace has surely outlasted its realistic service expectations, I would counsel you to replace it in July rather than January, when Murphy is most likely to have a hand in this matter. Return on investment consideration number one is whether or not the replacement is necessary.
Another important consideration is your personal situation. If you are 93 years old or otherwise unlikely to live in your house much longer, then any investment is probably unwise. You haven't said much about your circumstances.
Also, with forced air, the condition of your duct work can have a significant impact on efficiency. Call several pros now and get a strategy together for replacement even if you can't do it right away at least you'll know what you are up against and can plan accordingly.

[rif]

PRELUDE makes some excellent points.

As long as you're not getting the bottom of the bunch brands/uncommon brands, i think the most important aspect is the installer.  The best brand system isnt worth much if installed improperly. 

When getting estimates,  get a feel for the company.  Are they giving you a hard sell, do they only want to talk to you when your wife is there too - walk away. 

In addition to the warranty points above, what kind of support and maintenance do they provide?  Warrantees from the mfg probably only cover parts not labor.  You can likely buy a maintenance/labor warranty for about $200/year.