No, not all of the time. But, it is important that the power be operated properly.
WHEN THE SYSTEM IS IN USE
It is recommended that anytime your Envirolet® System is going to be in use that both the Fans and Heater be on.
SYSTEM LEFT FOR UP TO 2 WEEKS
If the system is going to be left for up to 2 weeks, the system should be switched to Fans Only operation (by using the 2-position neon or toggle switch, depending on the model, located on the Top Panel).
SYSTEM LEFT FOR MORE THAN 2 WEEKS
If the system is going to be unused for more than 2 weeks, the unit can be completely shut off/unplugged.