Smart Thermostat: Control your home's heating from anywhere using the ENGO Smart app, or by voice with Amazon Alexa and Google Assistant Wireless Thermostat: The ENGO E20i battery-powered thermostat (2 x AA, black) connects wirelessly to its receiver over 868 MHz. Wall mount it, or put it on a shelf with its stand, away from heat sources and direct sunlight WiFi Thermostat: Reliable 2.4 GHz WiFi built into the receiver, so no extra gateway hub is needed. Your router must offer a 2.4 GHz network App Schedules: Set your heating schedules in the ENGO Smart app and share control with the family. If the internet drops, the thermostat still works from its buttons Works With Your Heating: The black E20i receiver has a voltage-free relay (COM/NO, max load 16(5)A) for boilers and heat pumps with a volt-free thermostat input, pumps and valve actuators. Needs 230 V and a qualified installer Simple and Discreet: 80 x 80 mm thermostat with three buttons and a backlit display, available in black or white. Key lock with optional PIN, TPI or hysteresis control, heating or cooling mode, 5 to 35°C Radiators or Underfloor: TPI settings for radiators, underfloor or electric heating, and the receiver can wire to a boiler, zone valve or wiring centre, which makes the E20i a good option for retrofit underfloor zones in one app