How Does It Work?
Sunlight passes through glass, gets absorbed by a dark surface and heats a confined area, by exactly the same physics it warms the interior of your car on a sunny day.
Pipes filled with water, or a heat transfer fluid absorbs this heat, and circulates to a storage tank. Various configurations are described in Types of Collectors.
Unlike most solar electric systems, all soar water heating systems are ‘off grid’. The energy from the sun is stored and used locally. This is why it is important to size a solar water heating system to match you hot water use. In an over cast sky climate like western Oregon, solar water heating is predominately sized to match the domestic hot water demand in the summer. In clear sky climates like eastern Oregon solar water heating can make a significant contribution to space heating systems that use hot water. The insulated storage tank is just as important as the collector in making use of free and renewable sunlight for water heating.