drainbamage
The Poop Bag Guy
Well actually....
The transformer in the furnace is ALWAYS on. Until you cut power to the furnace itself (usually a red switch in the vicinity of the furnace, or flip the breaker), the transformer will ALWAYS be converting 120v to 24v (all of the furnace's circuitry is on the 24v side). However, the power that's being drawn is minimal until the thermostat switch actually closes.
This is referred to as "ghost load".
Correct, but by "turn off the furnace", she really just means "change the thermostat from Heat to Off." The furnace itself is left on the entire time, so her argument is moot.
And besides, if we were really that concerned about power consumption, there are much more obvious places we could start than the thermostat.
But, this is not "things about your spouses that annoy you"...unless you work with them, in which case, may God have mercy on your soul.