I guess I don't understand staged heat. I thought it meant that the backup strips came on in stages as the temp got colder to keep up with demand without using them all as soon as the heat pump became ineffecient. But what controls the stages? Do they need an outside thermostat? Does the inside thermostat do it? Does it require some optional equipment? I would like for the heat pump to shut down when it gets too cold for it to do any good. I want to be informed before I decide what to tell my professional how I really want it set up. He will be hooking up a White-Rodgers Comfort-Set 90 Series thermostat with outside thermostat. 3 1/2 ton CPLT-42 heat pump/air with AEPT 060-00C air handler with variable speed blower. All Goodman, and HKR-15 15kw heat. Can this be staged to come on 5kw at a time? What is the best set up?