Sensi Lite Smart Thermostat, Data Privacy, Programmable, Wi-Fi, Easy DIY, Works With Alexa, Energy Star Certified, ST25, Most Systems C-Wire Not Required, Except On Heat/Cool Only and Heat Pump SystemEASY DIY INSTALLATION: Do it yourself fast with a built in level and simple step by step instructions. Works with the HVAC equipment found in most homes COMMON WIRE REQUIREMENTS: Common wire(C Wire) required for heat pump and heat cool only systems. C wire not required on most systems SAVE ABOUT 23% ON HVAC ENERGY*: ENERGY STAR certified and packed with features that help you save money, including flexible scheduling, geofencing, remote access and