There is a point where the heating is great.... and that's when outside temps drop to low single digits. Why? My guess is the small ptc heater is engaged at that point to generate some heat for the heatpump to play with. When outside temp is 9-12 degrees it just does its best with heatpump only. One of the reasons I'm not so concerned about the MG have only a PTC, yup it won't be as efficient ,but it may well be more effective across a wider temp range.