I have a hot water heating system. The furnace heats the water in the small expansion tank, which goes thru pipes along the baseboards to heat the rooms. This same system also supplies the hot water to showers and sinks. In the cold of winter, average burning about 6 gals of oil per day to take care of these needs, and with ever increasing cost of oil, this gets expensive. My idea is that like one of these small electric immersion things that can put in a cup of water to heat it up. Could...