Technology advancements have made huge studies in energy efficiency. one of those innovations is the Heat pump water heater. A company out of Australia was one of the first I know to introduce these innovative water heaters. Now there is a add on feature....

www.buildingcredibility.com last newsletter issue featured the Air tap A7 as an inexpensive air-source heat pump module that can retrofit an existing electric or gas storage type water heater. efficiencies of 240% are quoted with the existing heating elements acting as the backup!  Location of the unit probably effects the efficiency I would imagine. you can get more information at www.airgenerate.com the company is out of Houston Texas. list price is around $499.00, the installation is a couple hours and the air  can be vented  to the garage for cooling and be an added benefit. GE plans to introduce their hybrid heat pump water heater and says the costs are going to be around $400 more than a standard  water heater. With today's energy costs rising this makes the option of these units more affordable and a much sooner payback. the company says this will save the average consumer $250 dollars per year  with electric rates around $.10 cents a KWH. More manufacturers will  be entering the market as well, so look for more updates..