Originally Posted by Stubbs

Another good reason for the 12V heater is so you can take it to the pit lane with you.

At some of the larger events, where you have to walk a significant distance from the pits, then wait for more than just a couple of minutes to start your race, the motor can cool off. If you have the 12V heater running off an extra battery in your starter box, you can keep the heater on until the very last minute.

Of course, there's a way around that too. Some of the guys that I race with took a little wagon and built a plywood platform on it. Under the platform was a 12V deep cycle marine battery and power inverter. They just put their cars on top of it, plugged the heaters into the inverter, and walked the hole thing to the drivers stand. Added bonus was it made toting all their stuff up to the track much easier, since they weren't carrying everything.

Of course, that means you'd have to bring a wagon, inverter, marine battery, etc...with you to the event. You'd also have the cost of purchasing all of that if you didn't already have it. For convenience, and probably a little less money overall (heater + battery) having a 110V and 12V is the ticket. I've got the 110V version, but I'll likely get a 12V as well, just so I can have it on hand if needed.