I had a Canadian Tire Motormaster "HotWash" heater for my car's wiper fluid and it worked very well. I put in summer fluid too early in spring and the freezing caused the mechanism to crack and be junked.
When it was working, I could feel the added electrical load on the engine.
Here's a recall for the device:
http://www.cbc.ca/consumers/market/r...08mar2006.html