Abstract: A user-friendly programmable thermostat is described that includes a circular body having a large central display surrounded by a ring that can be rotated an pressed inward by a user so as to receive user input in a simple elegant fashion. Different colors can be displayed to the user to indicate currently active HVAC functions, and different shades of colors can be displayed to a user to indicate an estimated amount of time and/or energy for reaching a target temperature. The thermostat is wall mountable and is made up of a head unit removeably mounted to a backplate. A locking mechanism can be provided so as to increase security against unauthorized removal of the head unit. The backplate can be adapted to be mounted on a wall so as to be level, for example by including a bubble level on the backplate. One or more vents are preferably located on the sides of the body, such as in a gap beneath the translatably mounted ring, and/or in a gap between the head unit and the backplate.

Abstract: A thermostat is described for controlling air temperature in a building. The time associated with causing the controlled air temperature to reach a target temperature is estimated and displayed to a user. Input from a user indicating the target temperature can be received and the estimating and displaying can be carried out in real time. The thermostat can be wall-mounted or the user input can be received and estimated time can be displayed using a remote device, for example that communicates wirelessly with other components of the HVAC system.