As someone who's used air source heat pumps for years, they were good to around 5C, at which point they would start to ice up and need heat pumped out to melt the ice. They were utter crap if you had any kind of winter conditions.
I'd love to believe that modern ones are better, but its hard to pull the trigger on them after years of suffering.
I currently have oil heat, and love it. Nice hot (not luke warm) air. And if the power goes out, I just fire up a generator and I have good heat, because the blower doesn't take much to run. Having been w/o power for stretches as long as a week during winter, that is a massive benefit over electric heat.
Many modern heat pumps are much better than what you remember. Some maintain their full rated BTU output to 17F, or in the extreme models, 0-5F. They usually output some percentage of full BTU at even lower temps.
The common Asian 'mini split' models also use variable fan speeds to maintain higher coil temps and have output air that is warm enough to avoid the 'luke warm' issue of heat pump coils on 'dumb' air handlers that blow full speed.
That said, for cold environments, a backup is often required to make up for the performance drop at very cold temps without massively oversizing the system. Hopefully, you have your oil furnace coupled to a heat pump or perhaps supplemental minisplit heads. That is the best of all worlds: the HPs can cover 80-90% of the load, only needing the oil for extremes. Oil is likely to hit 5 a gallon this year, like last, so it would suck to rely entirely on it.
Yes - we have a dual fuel system. HP is used when the temps allow it. As far as I can tell, it's not eonomic to run it below 5C, and certainly not comfortable.
I'd love to believe that modern ones are better, but its hard to pull the trigger on them after years of suffering.
I currently have oil heat, and love it. Nice hot (not luke warm) air. And if the power goes out, I just fire up a generator and I have good heat, because the blower doesn't take much to run. Having been w/o power for stretches as long as a week during winter, that is a massive benefit over electric heat.