Check out the thread Subject: Roof Mounted PW Vents Worth The
Electricity?

Thanks. Everyone seems to have a different opinion as to whether the fan is
worth the electricity.

As an experiement, I may try setting the fan's thermostat 5 or 10 degrees
higher, and seeing if that causes the fan to cycle on and off on a very
sunny day, rather than staying on for hours at a time. It would seem to me
that if the fan were actually making any worthwhile difference toward
cooling the attic's internal temperature (compared to just letting the
soffit/ridge vents do their work passively), then, if the thermostat were
set high enough, the fan should cycle on and off a couple of times on a
sunny afternoon than just staying on until the end of the afternoon. The
fan's thermostat doesn't seem like it has much of a differential between
on/off, so if it doesn't ever cycle more than once, then the fan isn't
cooling the attic much. If, even when set all the way up to 120 degrees,
the fan turns on, but still can't cool the attic enough to cause the
thermostat to cycle off and then on again a couple of times on one sunny
afternoon, then I question whether the fan has any real cooling benefit.

By the way, today I made the fan significatly quieter by temporarily
shutting off circuit breaker, and then bending some of the blades that had
been out of balance. It's still not super quiet, but is substantially
better than before I made the adjustment.

Jay