Programmable thermostat

The reduced cooling required during the day also decreases the demands placed upon the electrical supply grid.

Difficulty with usability in residential environments appears to lead to lack of persistence of energy savings in homes.

"[3] This is supported with studies by Nevius and Pigg,[4] Cross and Judd[5] and others and Peffer et al.[6] has a recent review of the topic.

In addition to potential increased energy consumption, digital programmable thermostats have been criticised for their poor usability.

It has been noted that the use of programmable thermostats is hampered by misconception about the setback feature, reducing the amount of heating or cooling in a building needs for a short time (e.g. at night or when it is unoccupied).

Two methods have commonly been used to operate it: [1] A separate, continuous source of 24 volts alternating current (24 VAC) is provided to the thermostat.

The periods are commonly labeled "Morning", "Day", "Evening", and "Night", although nothing constrains the time intervals involved.

More-sophisticated models will allow for the release of the hold to take place at a set time in the future.

The selection of which days are defined as the "weekend" is arbitrary, depending on the user's heating and cooling schedule requirements.

More-sophisticated models may be programmed to run the circulating fan for a brief 5- to 10-minute period in the event a heating or cooling cycle has not taken place during the previous hour.

Process control or industrial thermostat also makes sure that the temperature is very stable[14](for instance, by reducing first overshoot and fluctuation[15] at the end of the heating cycle) such that the comfort level is increased.