yourname wrote:


Hmm, for a $250 ANNUAL heating cost, how does going to 90% save me
$84/yr??




With a 60 percent furnace you are spending 250 bucks but only getting
150 worth of heat[250*.6] A 90 percent furnace would use 166 of gas to
output 150 worth of heat[150/.9] so 84 a year. 93 percent 5 bucks more.


I am NOT a person to disconnect, unseal, and remove an old unit (now
an 80% model), suport the AC plenum, put the new unit in, attach
gas, electricity, thermostat, plumb out the combustion exhaust air,
reattach to the AC plenum, and seal it all up. This is several
hundred dollars of installation costs.

the assumption in your post that you could not buy a 60 percent
furnace is that you are buying a furnace, thus the comparison is only
valid apples to apples, new furnace to new furnace, not new furnace to
nothing.

History is history. Can't take back a decision made 4 years ago.

Now its 80% to anything else.


20 years is just about average here with heating degree days of
1263. Rust is the most common failure mode. We just don't hardly use
them.


condensing furnaces should not rust


All gas furnaces will rust here. The rust is on the OUTSIDE of the
heat exchanger and it is due to our environmental conditions here, not
due to the condensation of the exhaust gas. www.hvacopcost.com, we are
in Zone 5, hot and humid.
In your climate a superinsulated house would be a better return, you
should never need heat. My moderately well insulated house does not
drop below 68 on a 32 degree night. could save the cost of the furnace
and the gas


We are agreed that R40+ in walls and ceiling has a better payback.

Still higher payback comes with a geothermal heat pump with EER near 30
and COP of about 5.