Heating water does not happen magically. You have to consume energy to heat your water and pay money to do so. There are things you can do to conserve energy though. The Amphiro a1 is a self-powered smart water meter for your shower. It helps you save save energy by showing your hot water consumption in real time.
Amphiro a1 does not require any batteries. It is powered by a generator that harvests energy from the water flow. The device display shows your current water consumption, the water temperature, and your energy consumption. It looks pretty easy to install. You will be able to track your shower data online. The project is on Indiegogo.