Naturally the same hot water produced for sanitary purposes can be used for space heating. Due to the relatively low temperature of solar energy systems, heating systems generally employ under-floor heating or Fan-coil type radiators rather than conventional radiators.

The dimensioning of the collector area and storage are adjusted accordingly to provide for the heat requirement. This can give rise to problems, however, because the greatest requirement for heating occurs in the winter months when the solar energy available is reduced. The potential scenarios are:

• The system is dimensioned in such a way that no overheating occurs in summer, but the percentage of heating substitution in winter is very small.
• The system provides significant solar substitution for heating requirements, but overheats or requires an additional cooling system in summer.

• Swimming pools: Using excess solar energy, the period of time when the pool can be used can be extended from 2 months to 4-5 months.
• Solar cooling: Using an absorption chiller, solar energy can be used in stead of air conditioning to refrigerate living, working or storage spaces.
  

By combining one of these two options with a solar heating system, the area of solar panels can be increased to provide around 50% of total heating requirements in winter without giving rise to overheating problems in summer.