T4: heat, 1 cool.
T6 Pro: 2 heat 1 cool (heat pump), 2 cool (conventional). 7 day programable.
T6 Pro WiFi: 3 heat, 2 cool (heat pump), 2 heat, 2 cool (conventional). Lyric App for anywhere control of your system. Works with Apple Homekit & Amazon Echo to take care of your home comforts. Requires C wire.