wrote:

Again, what is the over-the-counter cost for an ECM motor?

You won't need to spend $1000 for a controller either.

Without the controller to vary the speed based on optimum air
flow under a given circumstance the ECM probably won't save
you a dime.

ECM motors have a broader and flatter efficiency profile across their
load range vs fractional HP PSC motors. While it is true that
multi-speed PSC motors are very inefficient at low speeds, PSC motors
are not. Then again, many older furnaces have PSC motors with only 1
speed, so replacing them with single-speed ECM motors would make no
difference on apparent furnace functionality or comfort, but would
make a difference on running cost.

This document is very interesting:

http://irc.nrc-cnrc.gc.ca/pubs/fullt.../nrcc38443.pdf

They go so far as to measure the amount of ADDITIONAL gas needed to
heat a home with an ECM motor vs PSC. Why does an ECM furnace use
more gas? Because the PSC motor generates more heat, and a furnace
with an ECM motor must use slightly more gas to make up for the
missing heat source.

In fact, everything else being equal, a furnace with an ECM motor
needed to use 14% more natural gas vs a furnace with a PSC motor.

A furnace with an ECM motor being used during the cooling season will
clearly result in a cooler house because of less heat being dumped
into the house from the motor.

See also:

http://www.caddet.org/infostore/display.php?id=20879

"During the space heating test period, the ECM reduced the
average furnace electrical consumption from 9.29 kWh/day
to 2.38 k Wh/day, a savings of 74 %."

"energy from daily gas consumption rose 14 %, from an
average of 213.7 to 243.3 MJ/day."

Cooling Period Results:

"Using the ECM saved 48 % of the energy to propel the fan,
4 % of the energy for the compressor, 21 % of the energy
for the air conditioner (fan plus compressor), and 14 %
of the electricity used by the entire house.