Nick,

If you check the data, or measure it yourself, Strips cost 2 to 3.5
times as much per BTU as the heat pump. So you set back by shutting
off the cheap heat (Heat Pump Compressor), and recover by using the
expensive strip heat. Setback increases the electric bill if the heat
strips come on during recovery. In addition to warming the air during
recovery, you also have to warm the entire thermal mass of the house
and all it's contents. THAT is ia big part of the added power
consumption.

Here in Myrtle Beach, SC, a lot of homeowners are relocated yankees
(like me), used to setback. They setback in the winter and their
electric bills go up. They call me to check their system, I explain
proper operation, they stop using setback in the winter and their
electric bill goes back down. Happens every winter, many times.

Many heat pump setback thermostats lock out strips during the beginning
of setback recovery. On those, recovery takes a LONG time. After a
number of hours, the strips are allowed back on, recovery occurs and
electric bill goes up.

Note that recovery without strips only works in mild weather, so
setback efficiency depends on your climate. It does not work well in
my climate.

By the way, my wife, like many women, has to make several potty trips
to pee every night. If I installed another setback thermostat and her
tush gets cold on a regular basis every night, I will get the cold
shoulder when it comes to sex. That alone is enough reason not to use
a setback thermostat.

Stretch