Quote Originally Posted by BottomScratcher View Post
Like I said, it's an obvious question, but if the fresh air coming in is near freezing, then it's going to impact on the heaters ability to warm the air inside the car up.

I can't imagine the size of the 12V battery needed to power a 1000W heater. The only other heater I know of is what Skoda calls the auxillary heater, known more commonly in Europe as night heaters. They are nothing short of bloody marvelous if you're in a place where there are real winters. The car ones are adapted from Wabasto truck night heaters used by European truckies with sleeper cabs.

All they do is take a small amount of fuel from the main fuel tank to a burner unit that heats the engine coolant, then its own small, low power draw fan forces heated air into the car interior. They can be operated by an an on/off timer, so are great for snowy climes. Just set it to come on a couple of hours before you plan on driving and forget about scraping ice from windscreens, and getting a foot of snow off the car - giving the driver more time to dig out the driveway.
I used to have a webasto auxiliary heater on vw touran 2.0 tdi sport back in the UK (sadly not a model ever sold here). It couldn't be programmed but would boost the normal heater when the temperature was below 6 degrees. It was powered by diesel from the fuels tank. The only problem with it was that the exhaust outlet was located half way up the side of the car exiting just under the drivers door so you often got a blast of fumes when you opened the door.