Direct or indirect usually explains the way the water is heated.

Direct Heating System - This is where the water from the cylinder [storage tank] is circulated through the solar panel, heated by the sun and returned to the cylinder.

Indirect Heating System - This is where a heating fluid [not water] is passed through a coil in the cylinder similar to a heating element. The heating fluid passes through the solar panel then the flows through the coil and back up to the cylinder.

We only promote the indirect system as the fluid used is capable of reaching high temperatures and will not freeze in the winter months.

Our cylinders have 2 indirect coils, 1 for solar and the other for a secondary heating system. Our cylinders also have an immersion heater.