5. Drain Water Heat Recovery System

This technology is relatively old, but I have never heard of it up until now. I am surprised this system is not automatically installed when a new home is installed. Obviously there is a small upfront cost when installing, but the system will pay itself off in the long term.

Design Improvement

As mentioned in the video above, this system is only effective when taking a a shower because the drained hot water is pre-heating the cold water before entering the water boiler. So the system is not active when homeowners are taking bath. I don't think this system would be efficient, but perhaps bathtubs can also be made of conductive material and the dissipated heat through the bathtub can be used to also pre-heat cold water entering the water boiler. As of now, hot water from baths is dissipated into the air and is not used for anything.