Automatically figure out most economical setback temperature based on heat source, exterior temperature and duration

by Daniel Born: Depending on heat source (heatpump, aux heat, etc.) and setback duration (while sleeping, while at work, etc.) and exterior temperature, decide how low (with a configurable minimum) to allow setback temperature to go to allow for smart recovery to be back at desired temperature in time while saving the most money (allow entering energy costs for each heating source).