A controlled-environment plant growing systems are described. The system may include a plant growing enclosure, a liquid-cooled LED unit, an air cooler unit, an air heater unit, a heat exhaust unit, a recirculation pump, a chiller, and a controller. The enclosure may have mirror-like inner surfaces. The LED unit may include one or more LED modules and a transparent, liquid-tight housing encasing the LED modules. The housing may have a liquid inlet and a liquid outlet configured to flow a liquid coolant through the housing, thereby cooling the LED modules. The air cooler unit may be configured to cool the enclosure via the liquid coolant. The air heater unit may be configured to heat the enclosure via heat produce by the LED modules. The heat exhaust unit may be configured to exhaust excess heat remote of the enclosure. The controller may be configured to control one or more of the air cooler unit, the air heater unit, and/or the chiller in order to control the temperature within the enclosure.
