Lightstat's TG line of Light-Sensing Thermostats for landlords set back temperatures based on indoor light level. When the lights go down the thermostats automatically lower the heating setpoint or raise the cooling setpoint. When the lights are on, tenants can adjust the temperature only within preset limits, saving energy and money. Equipment is protected from damage and premature wear caused by overheating and overcooling. Temperature limits are built into the thermostats at the factory according to landlord or building management specifications. There are no batteries to change, no clocks to set, and no programs to enter. Installation is a snap because Lightstat thermostats replace conventional thermostats wire for wire. Models are available in heating only, heating and cooling, and heat pump configurations.