For their use, you need to have 12V power supply with power consumption from 390mA to 630mA. The power consumption varies depending on the heating mode that you choose. In fact the dew heater has a pressure switch that allows to vary the heating temperature from high to low. Also a led indicator is green color in the lowest temperature set and red color in the highest temperature set. The OFF LED indicates that the dew heater has no power. The power of the dew heater is through a female jack 2,5mm diameter.