I actually used https://www.ncei.noaa.gov/products/land-based-station/us-cli... for my city to develop a model for the cost of btus from either method throughout the year and the heat pumps cope at that hourly temperature, and it was slightly cheaper for heat pump for the entire year. But I also live in a marine influenced climate in the west with low electricity rates.
Whereabouts did that actually work? I can't think of a west coast locale where electricity is actually cheap and you get anything remotely resembling a winter.
I can see places like coastal california where you're on AC virtually year around and maybe need a day or two of heat.