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When setting back a thermostat might be a bad idea

Here is a heat pump scenario I just ran into that defies the common
conceptions about always saving money by setting back the heat at
night:

Daytime high 60 degrees
Nighttime low 15 degrees

Thermostat temp inside set at 67 daytime, back to 60 at night.

During the day, the heat pump is relatively OK, going on minimally
most of the time, due to solar gain through the windows and normal
household heat generating activities. The heat strips don't seem to
kick in. We keep it set at 67 until about 11 PM, when the temps
really start to fall, getting the most efficient use of the unit.

Dropping it down to 60 overnight allows the temp inside to drop to 60
and the unit goes on and off only a few times, with the heat strips
helping maintain the 60 set point.

However, cranking the heat back up at dawn puts the unit into trying
to go full blast, heat the house AND the cooled thermal mass, all at
the worst possible time, when it is 15 degrees outside. The heat
strips essentially do all of the heavy lifting before the outside air
temp can get up to a point that the compressor can work effectively.

If I was to follow the standard rules, our power bill would be high.
Instead, I inch the thermostat up a couple of degrees, and at the same
time start a strong fire in the fireplace, and crank on a couple of
burners on the propane stove to warm the kitchen. Later, about 11 AM,
or when the outside air is warmer, I'll return the thermostat to the
67 degree setting. I guess the alternative is to not get up until
noon...
 
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