Energy Smart Heater
There are a number of designs for the energy smart heater out there. Some of them are solar powered. A typical household solar heating system of this sort consists of a solar panel with a heat transfer fluid flowing through it.
The transfer fluid transports the stored heat energy to a household radiator or a water tank where it can be used.
Generally this heat transfer liquid is simply treated water. The solid panel is located somewhere where it can effectively receive direct sunlight throughout the day (generally on the roof of a building). The end process is heat taken from the panel and transferred to a storage container.
This is not the only form of an energy smart heater, however. Even if you don’t want to install an solar heater, generally speaking, newer water heaters are far more energy efficient than old ones, and you might consider an upgrade to an energy smart heater.