For decades the Japanese market has had access to this very efficient water heater and now the Sanden CO2 heat pump water heater is starting to take hold in the USA. The design of this unit gives better installation options, more efficient water heating, and long-term durability. Gone are the days of installing a water heater and writing the date on the tank to determine when we should start to live in fear of a failure. Check out this heat pump water heater.