@Bogleg, I did a little experiment today while waiting on my interval timer (due to arrive tomorrow or Tuesday). I manually switched my fan on and off from outside of the tent (ran the extension cord out of the tent and through a switched outlet) and measured energy usage over the course of that hour and the hours adjacent to it. My switching was irregular since it was manual, but I tried to approximate about 1/4 time on - that is, 15 minutes out of the hour in one- to two-minute intervals. The results are pretty encouraging. Remember that these include my LED panel light, heater, and exhaust fan. So turning the fan off will not only reduce the need for heat but will by itself stop using electricity.
Previous hour: 0.945kWh used
Sample hour: 0.429kWh used
Following hour: 0.956kWh used
So in my test case, I used less than half of the electricity that I’d used in the adjacent hours. Not terribly scientific, but encouraging nonetheless.