The one time I used one was when I fermented 3724 @ 90F for the first time, after realizing my fermwrap was toast. I wish I could find the heater - don't remember the wattage, but it was a heavy duty. It was summer and I put the fermenter in a plastic tote of 90F water, in an upstairs room with the AC vents shut - so the room temp was pretty steady ~ 80F. I put a sleeping bag over the top of the tote with the bucket to insulate. And it worked really well with that setup. I checked temps a couple times a day and it stayed between 90-93F. I didn't ramp given these temps, but the 3724 finished @ 1.002 in 12 days.