200W = 2 old fashioned light bulbs. I highly doubt that is going to have much impact in a real midwest cold spell.
Given that about any house wiring I have seen will run a 1.5kW heater, I don't see the problem.
With my F250 I have the block heater and the cab heater running on the same circuit. It works pretty well. Certainly takes a LOT longer to get going if I forgot to plug in when I get home.
Agreed, 200w won't work fast up north here in "real" cold - I was meaning for Dan to try it down in the Research Triangle (N. Carolina).
Rgds, D.