Self-Regulating Heat Tape will draw variable Power depending on the ambient temperature. It draws more power when temperatures are cold and less power when temperatures are warmer. However when the self-regulating cable is plugged in, it is always working, even if only slightly drawing power in warm temperatures. Adding the temperature-controlled switch like ThermaCord to plug-in heat tape or a Thermostatic Controller with Sensor to field assembled cable, will cut the supply of power to your Heat tape when it is not needed.
This will save you energy Costs.