On Apr 29, 11:03 am, "Buck Turgidson" wrote:
Don't know what vintage you are talking about, but I've never seen a
furnace with an exhaust blower that was only 60% efficient. Even a
run of the mill, cheap gas furnace has been 80% for decades. And
they have a lifespan of about 25 years.

http://hes.lbl.gov/hes/aceee/afue.html

Interesting site. They claim:

"If your furnace is 20 years old or more, it probably has an AFUE of
just 50 to 60%. By 1990, the typical efficiency had risen to 80%. Some
models today have an efficiencies of 95% or higher!"

So, from 1987 to 1990 the typical new furnace went from 50-60%, to
80%? I don't find that credible.

And if that ain't bad enough, how about this gem:

"The highest efficiency models can cost a little more up front, but
you'll save on fuel bills. You may have to shop around; some
installers may charge as little as $100 more for the high-efficiency
models, others charge a lot more. "

Anybody find that credible?