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.
Last edited by bridgman; 09/16/10 02:44 AM.
