It rarely gets below freezing here, so the heater was not really necessary at all. Nevertheless, I keep the tractor in the garage, which is also a workshop, laundry room, storage room...well, you get the picture. The fumes from startup used to fill up the garage and linger for some time. My wife asked me if there was some way to avoid this. I put in a block heater and now use it when starting at anything below +80F. This may seem silly to some, but it does eliminate most of the fumes and also makes for a much smoother start. For us, at least, it does seem worth it for the small cost.
When I lived in VT, I had a VW diesel Rabbit PU that I parked outside. I set up a HD extension cord, and ran it under and into the house (sealing the drill hole very well). I connected it to a setup in a broom closet where I could put the outlet on a timer or could turn it on or off with a switch. In winter, I always plugged the heater in when I got home, but the juice was off. If I needed to go somewhere early the next morning, the timer would turn the heater on a couple of hours before I needed to get up and leave.