In this Hot water heater, it takes the heat in the room and dumps it into the water. It is twice as efficient as a standard hot water heater. They claim that will save about $286 per year on your electric bill. The problem as I see it is that the unit costs $1500 not including tax and installation. It is eligible for a 30% tax credit (so you'll save $500). I believe that makes it 3.6 years to payback its cost not counting installation costs.
Since these have very similar 'guts' to a refrigerator, I would expect it to last just as long. I think when our water heater dies, we'll replace it with one of these.