It depends on the control module for the fireplace. Keep in mind that all a timer or smart plug does is interrupt the power flow to the device that's plugged into it. If your fireplace has a manual (e.g. a toggle) switch or the control module "remembers" your settings during a power outage, then you should be able to use a timer or smart plug. If not, a timer or smart plug will not work. The easiest way to find out is to turn your fireplace on, unplug it, wait 30 seconds and plug it back in. If it returns to the previous function, then a timer should work. If you have to use the control module or remote control to activate the fireplace again after the power interruption, the same thing will happen with a timer or smart plug.