Something quite isn't right, or I'm an idiot.... I put in $8.14 per "Unit" of natural gas (my current cost). One "Unit" of natural gas is 1000 cubic feet, which on the _low end_ contains more than 1,000,000 BTUs (in practice, it's more). That's $1068 doll hairs a year @ the 85% efficiency of "last generation" furnaces from yesteryear.
The newest Natural Gas furnaces are so efficient, that the exhaust pipe is just plain old PVC pipe, not metal, because nearly all of the heat is extracted. These run around 95% efficiency. Sticking that into the calc, that comes out to $971 blonde ones.
$1068 at 85% efficiency is $907 "effective" heating dollars. $971 at 94% efficiency is $912 so that passes a basic sanity check.
The major improvement is efficiency c es from runnimg higher volume at lower temperature differentials. This allows the "cold" side of the furnace/boiler to condense the water vapor in the combustion gasses and capture its latent heat.
The newest Natural Gas furnaces are so efficient, that the exhaust pipe is just plain old PVC pipe, not metal, because nearly all of the heat is extracted. These run around 95% efficiency. Sticking that into the calc, that comes out to $971 blonde ones.
What am I missing