Heat pump = conventional AC - (heat strip/gas burner) + reversing the refrigeration circuit for the heat cycle + efficient ECM motor (for air blower) + VFD comp

Heat pump = conventional AC - (heat strip/gas burner) + reversing the refrigeration circuit for the heat cycle + efficient ECM motor (for air blower) + VFD compressor (single phase to DC to three phase AC with variable frequency) + modern controls to manage both inside and outside motors. One can install an efficient AC unit with electric strips (gas burner) with "efficient ECM motor (for air blower) + VFD compressor (single phase to DC to three phase AC with variable frequency) + modern controls to manage both inside and outside motors." That's where modern AC units are driving at. Heat pump uses electricity for compressor fan and fan in that outdoor unit. In an efficient conventional AC unit, one trades the extra electricity used in the outside unit for the electricity used for heat strips. Geothermal heat pump is efficient and is a different ball game.