In the city of Barcelona all new buildings are obliged to include solar panels for the production of domestic hot water. In 1999 the Barcelona council passed a bylaw on the use of solar energy to tap into that resource. According to this bylaw, which is known as the "Ordenanza Solar" (Solar Bylaw), all new buildings and buildings undergoing major refurbishment are obliged to use solar energy to supply at least 60% of their running hot water requirements.

On the coast an extensive urban development and infrastructure plan is being developed. The project tries to promote a spirit of co-existence and co-operation between all sectors of society and promote a model of a sustainable city. At first the decision to impose realisation of the solar installations encountered substantial comments and discussions from all professionals involved. These were solved in a series of meetings. An inquiry revealed that 80% of the inhabitants of Barcelona are willing to pay 10% more for renewable energy. After the acceptation of the Solar Bylaw, visits by citizens to the local Renewable Energy Information centre doubled.

After the Bylaw became active in August 2000, within one year the total amount of square meters of solar thermal applications quadrupled. This means savings of 2.838 tonnes of CO2. Another interesting outcome has been that houses equipped with solar thermal appliances became relatively more valuable.

Now, a campaign is organised to replicate the project, this time aimed at involving all municipalities of the Catalunian region and supported by the Regional Governement. For succesful implementation of the campaign it was necessary first to define the local characteristics as housing typologies, energy consumption, solar radiation, legal frame etc. and defining costs, estimated production and savings. After this, answers were sought how to provide the necessary complementary or accompanying services (suppliers, installers, training promoters, architects, installers, municipal technicians). Finally appropriate financial schemes like conventional and green bank loans, leasing etc had to be found. All these data were gathered to compose a campaign proposal to municipalities and regional governments.

A quickly growing number of other municipalities have approved a solar ordinance based on the Barcelona's one, adapting it to their own characteristics. Also a number of other parties including UNESCO became involved in this initiative. To lift a initiative like this, a voluntary political decision has to be made and extensive support has to be pursued.