The efficiency of a heat pump can vary depending on several factors, including outdoor temperature, system design, and specific equipment used. However, in general, heat pumps are more efficient when operating in normal heat mode compared to AUX heat mode.
During normal heat mode, a heat pump extracts heat from the outdoor air and transfers it indoors to heat your home. This process is typically more energy-efficient than using auxiliary heat, such as electric resistance heating. Heat pumps can achieve a high coefficient of performance (COP), which is a measure of their efficiency, meaning they provide more heat output for the energy they consume.
On the other hand, AUX heat mode activates when the outdoor temperature drops significantly, usually below a certain threshold (e.g., 30 degrees Fahrenheit). In AUX heat mode, the heat pump relies on auxiliary heat sources, such as electric resistance heating or a gas furnace, to provide supplemental heat. These auxiliary heat sources can deliver heat more quickly than the heat pump but are generally less efficient. They consume more energy for the same amount of heat output compared to the heat pump.
In your specific case, if it takes about an hour for the heat pump to raise the temperature by 2 degrees, and only around 10 minutes with AUX heat, it suggests that the auxiliary heat source is capable of delivering heat more rapidly, but at a higher energy cost. The heat pump, while slower, is likely more energy-efficient overall, especially in milder temperatures. However, during colder conditions, the auxiliary heat may be necessary to provide quicker and more significant temperature increases, albeit with lower efficiency.
It's important to note that these efficiency comparisons can vary depending on the specific equipment, system settings, insulation levels, and other factors. If you have concerns about the performance or efficiency of your heat pump system, it may be best to consult with a professional HVAC technician or the manufacturer for more accurate information regarding your specific setup.