Is it interesting to only heat up with a reversible air conditioning?
Like any heat pump, an air conditioner is only really efficient for heating when the outdoor temperature is positive.
While it is possible to heat up with this system at significantly negative temperatures, the efficiency decreases with the cooling of the outside air, forcing the pump to provide stresses that can affect its longevity. Moreover, in this configuration, its energy efficiency drops and its operating cost increases.
This is why I am generally in favor of the complementarity of energies and means of heating, reserving the use of reversible clématisation at the least rigorous temperature periods. Complementary heating is welcome when it is very cold.