In the 80s decade there was made an important investment in solar collector technology in Portugal but some problems related with an insufficient developed technology and inexperienced installer firms have been created a negative image on the public eye. On the year of 2000, some studies

estimated that Portugal had installed 239 500 m2 of total collector area but many were not operational and never performed up to expectations. This value was quite distant from Greece (2 815 000 m2) and Turkey (750 000 m2) but quite equal to Spain (399 922 m2) and Italy (344 000 m2) [5]. The studies that have been elaborated by the Solar Thermal Energy Observatory since 2003, demonstrate that collectors market is been growing. The more recent study, from 2006, reveals that the collector area installed was 28 300 m2, an increment of 49% relatively to the previous year, estimating that total area installed in Portugal was 253 000 of m2 [6]. Small domestic systems represented 65% of the total market and multi-residential buildings were residual. It is true that solar collectors market is growing but is still very far from the 150 000 m2 /year ambitioned initially. Noticed that new regulations were enacted in 2006 and before that it was not obligatory to install solar collectors. We predicted that solar collector market is going to have the so long expected increment. It is proof that new regulations usually take a transition period of one or two years to be completely adopted by all parts.