Greetings,

I recently purchased a new Trane two-stage furnace and air conditioner.
I still have the old, non-electronic, non-programmable thermostat that
I have had for years (with my previous single-stage furnace). The HVAC
contractor said that it would be wise (but not required) to get a
programmable thermostat. His company actually sells/installs them, but
he said that I could save a lot of money by doing it myself.

As I've started looking into this, I'm a little confused about whether
to install a single-stage or two-stage thermostat. I understand that
if I get a single-stage thermostat, then the furnace will start up with
the first stage and go to full heat after 10-15 minutes. With a
two-stage thermostat, the thermostat apparently has control over the
starting and stopping of these stages. Is that right?

My existing thermostat has four wires coming into it. I assume that
I'd have to run more wire to use a two-stage thermostat. Is that
right? That would be somewhat of a pain, so I'm trying to gauge the
benefit of doing that vs going with a single-stage (but still
programmable) thermostat.

Any advice appreciated.