Each manufacture will have their own working conditions specs. They would be the best place to ask for information about their systems.

what temperature does the electric heater come on? That should give you some idea of what temperature the heat pump will need added heat

My neighbor says at less than -05°F he shuts the A/A heat pump down and uses the oil burner.

It depends of the working fluid. It have to be able to evaporate on the low temperature side. Some heat pumps can work at as low temperature as -5 C (~23F). The system can force the evaporation with lowering the pressure.

Some heat pumps can work at as low temperature as -5 C (~23F). The system can force the evaporation with lowering the pressure.

can you provide the manufactuere for this?? We will be replacing our heat pump in the near future and with the the one we have now the electric heating element comes on whenever the temperature drops below +32 F.

I didn't think that any heat pump worked below the freezing point of water?

Yes they do. My neighbor's run to -12C. (mine is geothermal, I don't have this problem) Ask for the Canadian heat pumps, they are made for colder climate.

When a manufacturer design a heat pump, he can balance the cooling and heating capacity. This is why it is important to buy one that is adapted to your climate. A "Florida" unit might be less expensive but will stop heating much earlier than the northern version.

Most manufacturers produce both versions. You might have to go through a northern distributor to get the right type though.

You might also consider a geothermal unit to save even more on electricity. More expensive to install though.

Please provide your location. The decision properly made is not based upon temperature, but rather the climate of the location.

There will always be days when the auxilliary coil is needed. But the question is how often in winter does the temperature drop below the ability of the pump to work without the auxilliary coil.

A good rule of thumb in the eastern US is that these things don't work well north of Washington DC/Baltimore/South Jersey.

Sure there will be days in winter when the temperature is seasonably mild, but not often enough to justify the capital cost of the unit.

If the payback period is more than 5 to 7 years, this alternative is a poor one.

You need to do a cost analysis to determine the annual cost over the life cycle and compare this cost to other viable alternatives.