Originally posted by marca
In my opinion, it is a waste of both electricity and heat pump wear and tear to operate a system in this fashion at low temperatures. That is the reason I switch OFF the heat pump and switch ON the resistance heat during periods of low outside temperature. My logic is; if the heat pump is unable to satisfy within a reasonable period of time, then it should not be running. Makes sense?
It's your opinion. Just doesn't make it right nor does your logic make sense.

A heat pump provides useable heat well below 20F, and it costs more to run strip heat only.

Sit down and do some math. You'll need the following information: BTUH capacity of your strip heat; running amps of your strip heat; running amps of your heat pump; BTUH output of your HP; KW-H cost; heat loss of your structure at 20F.

Now see what's cheaper to run. I bet you'll find that the HP running continuously with b/u heaters bumping intermittently is significantly cheaper than only running the b/u heaters.

I've done the math. I want you to see for yourself.