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 ou

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.