Some modern heating and cooling systems require special controls. Heat pumps are the most common and usually require special setback thermostats.

When a heat pump is in its heating mode, setting back a conventional heat pump thermostat can cause the unit to operate inefficiently, thereby canceling out any savings achieved by lowering the temperature setting. Maintaining a moderate setting is the most cost-effective practice.

Recently some companies have begun selling specially designed setback thermostats for heat pumps, which make setting back the thermostat cost effective. These thermostats typically use special algorithms to minimize the use of backup electric resistance heat systems.

In its cooling mode, the heat pump operates like an air conditioner; therefore, manually turning up the thermostat will save you money.

Electric resistance systems, such as electric baseboard heating, also require thermostats capable of directly controlling 120 volt or 240 volt line-voltage circuits. Only a few companies manufacture line-voltage setback thermostats.