A solar combisystem is a solar heating system that provides both space heating and hot water from a common array of solar thermal collectors, normally linked to an auxiliary non-solar heat source. Solar combisystems may range in size from those installed in individual properties to those serving several in a block heating scheme. Those serving larger groups of properties via district heating tend to be called central solar heating schemes.
Following the work of IEA Task 26 (1998 to 2002), solar combisystems can be classified according to two main aspects; firstly by the heat storage category (the way in which water is added to and drawn from the storage tank and its effect on stratification); secondly by the auxiliary heat management category (the way in which non-solar auxiliary heaters are integrated into the system).
The size and complexity of combisystems, and the number of options available, mean that comparing design alternatives is not straightforward. Useful approximations of performance can be produced relatively easily, however accurate predictions remain difficult.
Solar combisystems use similar technologies to those used for solar hot water and for regular central heating and underfloor heating, as well as those used in the auxiliary systems - microgeneration technologies or otherwise.
By the end of the 20th century solar hot water systems had been capable of meeting a significant portion of domestic hot water in many climate zones. However it was only with the development of reliable low-energy building techniques in the last decades of the century that extending such systems for space heating became realistic in temperate and colder climatic zones.
