I would love to ditch my C4 tstats. Having to open a different app, ie Nest, is no big deal. My problem is the programming I have relating to the t-stat, ie announcements if a door/window is open for 5 minutes saying the AC is on and door/window is open. BUT, if I have a t-stat that can take advantage of the high efficiency settings, the savings may be worth it. BUT, maybe things are not hooked up and/or the settings like what ILOVEC4 posted are wrong. My wiring is fine.