This system is also referred to as a batch heater
This system is also referred to as a batch heater and a breadbox. It consists of an approximately 40-gallon insulated tank, lined with glass on the inside and painted black on the outside. It is mounted on the roof, or on the ground in the sun. Plumbing from the house supplies the box with cold water through an inlet that extends down to the bottom of the tank. The box itself acts like a collector, absorbing and trapping the sun’s heat and heating the water. An outlet supplies the house with heated water from the top of the tank