We recently moved into a 1,600 sq ft home in central Illinois that is equipped with a Goodman GSH 130130IAB heat pump. (It has a SEER rating of 13 and a HSPF rating of 7.7) The backup/auxiliary furnace is an electric Goodman ARUF 303016AA. Both units were installed during construction, approximately five years ago, and to the best of my knowledge have never needed repair. Our old house had a forced air, natural gas furnace so we’ve no experience with heat pumps. Shortly after moving in our neighbor warned us that in winter his heating costs skyrocket and his heat pump runs almost constantly. This week our nightly temperatures have been dropping into the low 20’s and I’ve noticed the pump running for hours at a time with only brief shutdowns between cycles. After doing some research I’ve learned that some heat pumps will automatically stop in favor of the Auxiliary heat when the temperature drops below the point where they are efficient, but I don‘t believe mine is that sophisticated. It seems the Auxiliary heat only operates when the thermostat reads the temperature as 2 degrees below the SET temp. or when it is manually switched over to AUX. heat only. Does any one know at what outdoor temperature this model will use more energy than is saves. We didn’t receive an owners manual, all I can find on-line are technical info. & installation instructions, and the service company that the H.O.A. recommends wants >$100 to come out for a routine inspection. The units seem to be operating fine we’re just trying to find out the most efficient way to operate them.