Coleman heat pump and heating element together

My 15k Coleman heat pump with heat strip is 12 years old, so YMMV.

When calling for heat, the unit runs either the heat pump OR the heat strip. The switchover outside temp is "approximately" 40 degrees F, and the stated reason for that temp is to avoid the outdoor coil freezing. For heat output comparison, the heat pump provides 12,700 BTUH heating at 47 deg F. The heat strip provides 5,600 BTUH.

Switching from factual to editorial mode, like most heating devices, the heat strip when not in use gets covered with whatever is floating in the air, and stinks like crazy when first used after a long time of no use. When I de-winterize, I always run the heat pump in the driveway until the smell goes away. Assuming it's reasonably warm when you de-winterize, you aren't able to run the heat strip because it's conveniently automatic. The end result, especially if the heat strip hasn't run for a few years, is this: A below 40 deg day comes along, you run the heat, the heat strip runs, and the stink is so bad you want to open the windows to let it out. Happened to me the first time when it was well below freezing outside. I addressed this by adding a switch to the heat pump so I could manually force the heat strip to run, and de-stinking it is part of the de-winterization process. Doing this is not for most people obviously.

The heat strip might not provide enough output to be your only heat source in the below 40 deg weather where it's switched on. It has roughly the same output as a 15 amp portable heater. I use it occasionally, and my overall conclusion would be to get it if it doesn't add a whole lot to the price.

From RVP For MANUAL ceiling controls NOT wall tstats

The heat pump will operate on reverse cycle refrigerant
heating at outdoor temperatures above freezing. When the
outdoor temperature is below freezing, the heat pump
compressor will shut down to prevent outdoor coil freeze-up.
At this time, the optional electric resistance heater will be
utilized to take the chill out of the indoor air. The electric
resistance heater is not a substitute for a furnace at these low
outdoor temperatures.

I added a 2nd thermostat for the wall for the furnace only. So I can use the heat strip and the furnace together, rather than "either/or".

I find I can use the heat strip down to about -20 c (-4 f). Below that the fan on the air conditioner doesn't like it.

Thanks for all the information! My old Dometic air conditioner has a heat strip, so I'm familiar with what I think of as the burned dust smell, and also with how much heat to expect.