What in the heck is a furnace?

The opposite of an air conditioner

What we *really* need is something that could, for example, pump some of the heat out of Rick's house and into my house.

Adrian, if your current furnace is *really* old it could be considerably lower than 80% efficiency (I think the norm was about 60%), in which case the savings could be higher... but the savings from even a basic new furnace (80% efficiency is the lowest I have seen for a while) would be proportionally higher as well.

There seem to be two levels of "troublesomeness" - first level is from replacing the pilot light with electronic ignition, adding a blower (to the air intake, I think), and that's pretty much it. That seems to be enough to get you to the high 80s in efficiency.

Next level of complexity is extra heat exchanger capacity, enough to cool the exhaust air low enough that water condenses out, mixes with the flue gases to get a bit acidic, and drips down to the bottom of your furnace and out a hose. You also end up replacing your current chimney with a plastic pipe, and typically add another pipe for intake air. That was what made me think my furnace was just too damn fancy.

As a starting point I would try to get an estimate for how efficient your current furnace is. That will let you make some reasonable estimates for how much you can save at each efficiency level / price point.

What's an air conditioner?

Nice avatar Cam.

I guess the main question is, how efficient is my existing furnace? if it's 80% I won't bother, but it's possible it's not as good as that, in which case it may be worth the change. I'd like to sell the house in a year or so....on the one hand, a new furnace might be an unnecessary expense, but on the other it may be a selling feature.

Thanks for all the feedback, everyone.

AFAIK the big selling feature is "new" furnace, not "fancy" furnace.

Only people like us care about furnace technology or look at the efficiency specs

Whadya mean people like us?

Most of my experience is with oil fired units but I have replaced a few gas units and all were replaced due to heat exchanger failure. How old is the unit you have now? Gas / LP fired furnaces are not typically designed with much of a life expectancy. The heat exchangers fail over time and flue gasses start to mix with the air supply that is routed through the home. There’s also not a great deal of adjustability with the burner on gas units either. With some units, you can’t adjust anything. If you are serious about replacing your furnace, take a look at Lochinvar. They make some extremely efficient units approaching 100%. Their gas fired Knight Boilers are amazing. Their water heaters are pretty slick too.

Hi, Michael. The unit(Lennox) is a good 18 yrs old now and has been extremely reliable though perhaps not overly efficient... I recently installed a new water heater btw.