I have recently bought a home with a Rheem 10 seer heat pump system. I am assuming its 8 years old being the house was built in 2002. I am not really familiar with heat pumps. However, I have just received my second electric bill and it went from $175 for Nov. - Dec. to $705 from Dec. - Jan. I live in Kentucky, and it has been colder than normal probably 5 degrees colder for the Nov-Dec months. Not enough to really offset the $500 difference. The problem I am having is the upstairs system seems to not go into Aux heat all the time, just here and there and keeps the temp damn near its set temp. The downstairs unit, however, always has the red light on showing auxiliary heat. Even when its not running and just starts up at 1* less than the setting it goes right in to the auxiliary heat. Now I know Heat pumps were made to be more efficient and they lose their efficiency when the weather gets extremely cold but the $700 electric bill for a 2400 sq. house seems kind of out of whack. Outside the one unit's line is warm, where as, the other units copper line is very cold with ice on it. I have a feeling it could be low on refrigerant but I am not sure if that would cause the this kind of energy consumption. I am going to call a service tech, but I want to have as much info for him b/c I have heard to many horror stories about techs coming out and screwing things up on heat pumps. If any of you have any ideas what could be wrong causing the huge electric bills I would appreciate it.