Requires a 20A circuit(Connect 20A adapter or breaker),with 1.5″ outlet , min 0.35MPA pressure,suggest work with at least 0.25HP,suitable small bathtub & spa tub /hot tub 2 KW /110V-120V.No plug, just 3 cables,Black Cable is Live,White Cable is Neutral,Green Cable is Grounded. Adjustable thermostat from 0 – 45 °C, when the water temperature reaches the set temperature,it will stop automatically. when temperature is dropped down, it will heat up water until your set temperature. Thermostat case is engineering plastic, heating element using UL approval metal pipe electric-heating element, Incoloy800 against high temperature and against causticity dedicated stainless steel pipe.