On Tue, 15 Sep 2009 19:43:46 GMT, (GregS)
wrote:

I think the mechanical actually actually saves heating costs because
it does not cycle as much buy the fine tune digital will feel a lot
more comfortable and you may not have to set the temperature
as high or low.

Many (most?) digital thermostats attempt to control cycle rates also,
either by a temperature spread setting (mimicking the hysteresis of a
mechanical thermostat), or a predictive cycle count (i.e. let the temp
spread a bit more to get N cycles per hour. That's a setting on
ours)

And some thermostats "lie" to you -- the new Honeywell thermostats
installed with our AC upgrade seem to round the "current" temperature
more generously when it's close to the setpoint (e.g. if setting=73,
anything from say 72.1 to 74.5 is shown as 73, but if I change the
setting to 71, all of a sudden it's really 74 in the room :-) I think
it cuts down on complaints, and truthfully the whole AC system works
so much better than our old one well that I don't care (and I'm
usually very sensitive to small temp diffs).

Josh