I now use veriac controllers on my fan. You wont find it there. The reason is a fan controller uses full amperage but turns it off as it runs (for lack of a better way of explaining it) A veriac may cost 100 bucks but you control the wattage going to the fan. My small tent runs at 26 volts instead of 115 so it takes 1/4 or so of the power needed and it is not as hard on the fan. Fan controllers suck a lot. I have 2 of them for other places but i run the vortex full out. My grow is 2 weeks out and full out in a 4 x 4 i am at 45% RH which works for flower
So my 200 watt timber full blast with the fan and the inside fan uses a whopping 250 watts. With a fan speed controller it would be 75 watts more than that.
But those speed controllers work until you can get a veriac. For me it is all about efficiency. How cheap can I produce great buds. I am getting close to perfection. I used to strive for 95% but I will try to get to 98%
the law of diminishing returns is a BITCH though.