European Solar Thermal Industry Federation

Solar ordinances

Solar ordinances are regulations requiring that solar energy provides a minimum share of the heating demand.  Usually, they apply to new buildings, those undergoing major refurbishment and sometimes when the heating system is being replaced.

A decade ago, the idea of making the use of solar or renewable energy compulsory sounded radical and politically unrealistic in most parts of the world. However, solar obligations have now been adopted or are being discussed in a number of countries, regions and local authorities in Europe and beyond.

In June, 2007, while discussing the contents of the future EU Directive on Renewable Energies, the ITRE Committee of the European Parliament called on the Commission to "speed up the widespread adoption in all Member States of best practice regulations making it compulsory, at least where existing buildings are substantially renovated and new buildings are built, for a minimum proportion of the heating requirement to be met from renewable sources, as it already is in a growing number of regions and municipalities".

Solar obligations are probably the single most powerful tool for promoting the use of renewables in new buildings.  Practical experience shows their  numerous  benefits. However, solar obligations fundamentally change the way in which the solar thermal market grows and customers will often search for the cheapest possible solution. Therefore, solar obligation must include appropriate quality assurance measures.

A comprehensive study on solar regulations

Here you can download the main study best practice regulations for solar thermal 
(61 pages, last update August 2007, 868 KB).

This study includes following sections:

Reduction of administrative barriers

    Solar obligations
    - A short history of solar obligations
    - Benefits and costs
    - The need for quality assurance measures
    - Structure for a solar obligation and guidelines
    - Flanking measures Annexes
    - 27 years of solar obligation in Israel
    - Solar obligations in Spain
    - The debate on solar obligations in Germany
    - Solar obligations in Italy
    - Solar obligations in Ireland
    - Technical specifications for solar obligations

Solar regulations in different countries and regions

Spain (national level)

The Spanish government adopted a new Technical Building Code (CTE, Codigo Tecnico de la Edificacion) in March 2006 which includes an obligation (since September 2006) to cover part of the domestic hot water (DHW) demand with solar thermal energy. This obligation applies to all new buildings and to those undergoing major refurbishments.

The required solar contribution varies between 30 and 70 % depending on three main factors:

  • domestic hot water demand of the building (liters/day)
  • climate zone
  • conventional fuel to be replaced (only for refurbishments)

Some exceptions are defined in the law, mainly in the case of buildings that either satisfy their DHW demand by other renewables or by cogeneration or for shaded buildings.

It is important to point out that the municipal solar obligations, approved in the last few years in dozens of Spanish municipalities, including Barcelona in 2000 and Madrid in 2003, remained in force as long as they were stronger than the national obligation included in the CTE.

The effects on the market have been partially offset by the unexpected slowdown in the Spanish construction market in 2008 and 2009. However, solar obligations became a driver in the Spanish solar thermal market since estimates show that over 80 % of installations were motivated by CTE or municipal ordinances.

Further information on the new Spanish building code (CTE):

An extensive analysis of the solar obligation in the CTE can be found in the main study best practice regulations for solar thermal mentioned above.

Barcelona: the pioneer of solar regulation in Europe

The City of Barcelona has been the pioneer for Solar Regulations in Europe. The first Solar Ordinance came into force in 2000 and required that a certain share of the domestic hot water demand be supplied by solar thermal, in new buildings and those undergoing major refurbishment.

The implementation led to a significant increase in the use of solar thermal, thereby even stimulating the market for buildings not covered by the ordinance. The regulation was popular with decision makers and received widespread public support. Therefore, the number of buildings targeted increased and procedures, architectural integration as well as quality requirements improved thanks to the revision approved in 2006

As a part of the Solar Thermal Action Plan, developed within the K4RES-H project coordinated by ESTIF, the Barcelona Energy Agency published an analysis of the lessons learned during the implementations of the barcelona solar regulation:

An extensive summary in English of the in-depth study can be found in the Annex 2 of the main study best practice regulations for solar thermal mentioned above.

Madrid and other municipal solar regulations in Spain

Inspired by the positive experience of Barcelona, dozens of municipalities under administration of different political colours approved solar obligations all over Spain. 

The Spanish national Energy Agency IDAE actively promoted this trend by providing technical and legal advice to the interested municipalities. As a part of the Solar Thermal Action Plan, developed within the K4RES-H project coordinated by ESTIF, the Barcelona Energy Agency published a study of the experience drawn from the implementation following of the Soalr regulation in Madrid:


Israel is the country with the oldest solar obligation, in force since 1980. The law's success has made it largely superfluous: today, more than 90% of Israel's solar thermal market are in the voluntary segment, like installation on existing buildings, or systems bigger than required by law. Economies of scale, widespread awareness and training led to cost reductions. Typical payback times are around three of four years. People consider solar thermal systems an obvious component of buildings.

For more information on Israel, see Annex 1 of the main study best practice regulations for solar thermal mentioned above.

Germany: solar obligation as element of urban planning in the town of Vellmar

The City of Vellmar set the installation of solar thermal system as a preliminary condition for the authorisation to construct in a new development area.  Meanwhile a large number of houses have been built there.

As a part of the Solar Thermal Action Plan, developed within the K4RES-H project coordinated by ESTIF, the Energy Agency of the region of Kassel, Energie2000 studied the implementation of this solar regulation. Following materials (in German only) are available:

The German Federal government, as well as the government of the State of Baden-W├╝rttemberg are currently discussing the introduction of renewable heat obligations. 


Following the example of the town of Carugate, local solar obligations are in force in a number of small municipalities around Milan. A municipal obligation is in advanced state of discussion in the City of Rome.

At national level, a renewable heat obligation is included in the latest version (29.12.2006) of the law implementing the European Directive on the energy performance of buildings. It prescribes that at least 50% of the annual domestic hot water demand will have to be covered by renewable energy sources, whereas in the city centres with historical value this share is reduced to 20%.  The obligation will apply to new buildings, major renovations and in case of replacement of the heating system. 

However, the provisions about the renewable heat obligation are not yet applicable, because the implementing decrees have not yet been adopted. 

For the national renewable heat obligation to have a real effect, it is necessary that the implementing decrees are adopted and that they contain clear provisions effectively ensuring a high rate of compliance. Otherwise, there is the danger to replicate the experience of the law 10 of 1991, that was very demanding on paper but to a large extent was not observed in practice.

For more information on Italy, see Annex 4 of the main study best practice regulations for solar thermal mentioned above.


Starting at the end of 2005, a number of Irish local authorities introduced building energy standards as part of planning requirements in their jurisdiction. These building energy standards require a substantial increase in the energy performance of new buildings (between 40% and 60% reduction in energy usage) as well as a mandatory contribution of renewable energy to their thermal energy requirement.

For a two page  summary, please see Annex 5 of the main study best practice regulations for solar thermal mentioned above.

A 19 pages case study on the Irish solar regulations can be downloaded here.


And neighbouring Portugal quickly followed the Spanish example with their own regulation. The new Portuguese buildings code includes an obligation to install solar thermal systems or some other form of renewable energy providing a similar energy saving. The obligation only covers certain buildings. Amongst other restrictions, it applies to buildings with a South-East to South-West oriented roof surfaces. The solar system should have a minimum dimension of 1m2 per person assumed occupancy in the building.

For more information on the new Portuguese building code:

Solar Ordinances











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