To reduce the power consumption on heating water to nearly 50% the most economical option and smart option will be heat pumps. They work on the concept of air conditioner but with a difference, they use warmth for atmosphere and grounds from outside to heat the water within the house. As the heat from outside is used, the power consumption is limited. These geothermal heat pumps from Rheem are the smart options for green homes.
For more details:
http://www.sanicon.in