AZ Nomad wrote:

Just wondering if anyone has replaced their conventional furnace
/ HVAC fan motor (PSC, single phase, etc) with one of the new
ECM motors to realize a reduction in your electricity bill.

You'll never recoup the cost. Wait for the unit to wear out and...

Conventional small AC motors (fractional HP motors) are VERY
inefficient at converting electricity into motion. I've seen numbers
around 50% efficiency.

Many new furnaces today come with ECM motors because furnace fans run
longer (higher duty cycle) in modern HVAC systems today vs 20+ years
ago.

If the cost of an ECM motor is, say, less than $200 (for the
do-it-yourself-er) then it's highly likely that just replacing a
conventional AC motor with an ECM motor in an existing furnace would
pay itself back in 1 to 2 years - plus you have the existing motor as
a backup if or when the ECM motor breaks down.

If the entire unit is hopelessly inefficient,
then retrofitting makes no sense;

There are many mid-efficiency (80%) furnaces out there that DON't have
ECM motors, and there are many older furnaces that with simple
additions and modifications to intake and exhaust ducting (and by
turning down the burners and adjusting the burner primary air baffles)
can bring them to near 80% efficiency. You can convert a 30-year-old
60% efficient furnance to closed-combustion with some ducting and
modification to the cabinet's venting for example.

Does anyone know what the "over-the-counter" cost is of
these motors?

Does anybody know how to use a web search tool?

Nobody's posting any over-the-counter or "cash'n'carry" prices for
these motors on their websites.

I don't think too many of them are being sold for retro-fit or
non-HVAC systems.

In fact, there may even be supply shortages such that all production
is going straight to HVAC manufacturers.

Also, do ECM motors generate electrical or RF noise that is
either radiated by the motor or fed back into the household
wiring, thereby messing up AM radio reception?

Probably not; the motor is likely to be inside a metal housing.

My experience with electronically-controlled, variable-speed AC motors
(that you find in some treadmills and science-labs fume hoods) is that
they are extremely noisy (EM/RF noise) and without a lot of filtering
they inject a lot of noise back into the main supply wiring.

If there is a lot of high-current switching going on inside an ECM
motor, then I would think they too would be electrically noisy.