Abstract: Improvements to an HVAC thermostat include a fuel control module that estimates a rate of fuel usage by the HVAC system and issues a warning and optionally schedules a fuel delivery or solicits a fuel delivery bid when the on-site fuel supply drops beneath a predetermined level, a nightlight module that illuminates a touchscreen in accordance with at least one nightlight parameter, and a user interface mode control module that selects for display on the touchscreen display, a primary user interface from among a plurality of potential user interfaces based at least in part upon the frequency of use of each of the plurality of potential user interfaces.