Active solar thermal systems use a pump, valves, and a pump controller to move the liquid around the system. This obviously requires electricity to operate. The pumps on this type of system pressurize the liquid of the system.

These types of systems are more popular in colder climates because of the freeze factor associated with passive systems. Active systems usually have the storage tank inside the structure, and can completely drain the outside portion of the system so it will not freeze during extremely cold times.

Active systems are significantly more efficient than passive systems, but are also more expensive, and more difficult to install.