Active systems operate on the same principles of thermosiphonics, except that the storage tank is situated away from the panels. The main advantage is that the tank can be located in a space that is out of sight, and even in an insulated location, reducing heat loss and improving efficiency.

Active systems are the most popular solar thermal system

This system requires a pump and controller to get the cold water from the tank to the panels for it to be heated. These systems are a little more expensive to install because of their complexity. However, the price premium is outweighed by aesthetics – with only the panels being visible – and active systems are the most popular solar thermal system.


  • All systems integrate a supplementary heat source – electricity, gas or oil – for times when the skies are overcast, with reduced solar penetration.