The simpler option for solar thermal space heating is to install what's known as a "dump" system. In this setup, there is no storage tank: the collectors heat the domestic supply when the sun is shining and send that heat to some kind of liquid-to-air interface, such as a radiator, a baseboard heating unit or a fan convector.

There's one question that most people immediately ask: why would you install a space heating system that only works when the sun is shining and is therefore generating heat? They ask this because of the common misconception that solar energy only works when the sun is shining bright and strong, on cloudless days. The reality is that even diffused sunlight contains a great deal of power, if it can be harnessed.

In other words, a dump system is a valid choice because the sun may be shining enough to heat an efficient solar collector array (and from there the space heaters) even though it couldn't directly warm the building unaided.

Dump systems are often installed as a shunt load for a combined system: any heat generated that is not used to keep the domestic hot water supply nice and warm is pushed to space heaters to reduce heating costs.

A solar thermal space heating installation with no storage has the collectors angled to maximize the winter sun's energy – a very steep angle that also helps keep snow off. This means their output will fall off in spring and summer, when less heating is needed. The array should be sized to heat the building on an average winter day – don't size it too large or you'll overheat the house or the system itself.

No-storage dump systems for space heating can be set up as a drainback or pressurized system.