Oxford study proves heat pumps triumph over fossil fuels in the cold::Published Monday in the scientific journal Joule, the research found that heat pumps are two to three times more efficient than their oil and gas counterparts, specifically in temperatures ranging from 10 C to -20 C.
Here in Massachusetts, the belief is that heat pumps do not heat well when the temperatures reach 0F
That’s -17.8 C, so pretty close to the limit mentioned here