Efficiency is a misleading word for heating, because the units don't match; they are both energy, but different "type".
The denominator is fuel energy lost, but the numerator is thermal energy change within an area of interest.
A heat pump moves thermal energy from outside, changing unimportant thermal energy into good thermal energy.
"Coefficient of performance" is a better term.
https://en.m.wikipedia.org/wiki/Coefficient_of_performance