The excellent solar energy availability in Portugal, with global horizontal irradiation between 3.41 kWh/(m2.day) and 5.08 kWh/(m2.day), gives Portugal the opportunity to decrease its traditional dependency on energy imports. The imports are coming down in the last years mainly due to wind energy contribution, but also due to a combined contribution of energy efficiency measures and other renewable energy sources such as large hydro, biomass and solar. Since 2010 the country's dependency on conventional energy imports has been below 80%. It reached a maximum in 2017 of 77.7%. In 2021 the value was 67.1% (General Direction of Energy ).
The large solar resource has always been an incentive to use solar thermal collectors and systems, which was initiated in the seventies of the last century.Over the years, public policies mainly gave fiscal incentives to the installation of solar thermal systems for Domestic Hot Water (DHW) preparation. Despite these incentives, the total collector area installed until 2000 was 219 500 m2 .
In the first decade of this century, public policies were implemented to profit from this resource but imposing the “quality” paradigm in the technology and system installation services. In 2001 a program called “Solar hot water for Portugal”  was implemented, and it introduced the following certification schemes:
for solar thermal collectors and systems, in a very similar way to Solar Keymark, which was also implemented at the same time at the European level;
for installers of solar collectors and systems.
In 2002 the Directive 2002/91/EC of the European Parliament and the Council on the energy performance of buildings was published and the work of transposition to the Portuguese law was initiated. Benefiting from the work performed in the frame of the program “Solar hot water for Portugal” the transposition of the directive introduced the obligation to use of solar thermal collectors for hot water preparation in new buildings and large renovations. This obligation was accompanied by the following criteria: only solar thermal systems with certified collectors, installed by certified installers and having six years guarantee, could be accepted in the framework of this obligation.
These policies were important for growing the solar thermal market. Some fiscal incentives were also a good support to the growth of the market. Fiscal incentives were directed to families with deduction in the individual income tax but also to corporate income tax (during a few years, a very beneficial condition was possible: amortization of investment in renewable energies could be done in four years).
In 2009 a strong incentive program (http://www.paineissolares.gov.pt/faq-mst2009.html) busted the market's growth, especially in the domestic sector (the price of solar thermal systems for family houses could be acquired with a reduction in price from 30 to 60% depending on the typology and size of the system). A deduction in individual income tax could also be applied. In 2010 the incentive was directed to the social-service sector, but the financial crises stopped this incentive in the following years and also stopped the fiscal incentives).
In 2020 a new incentive program, “Programa de Apoio a Edifícios Mais Sustentáveis (PAE+S),” aimed to support to more sustainable buildings was launched and was open until 31st December 2020. In this program, support for installing Solar Thermal Systems for Hot Water Preparation was considered. The systems had to be Class A+. Support up to 70% was considered with a maximum of 2500€. The program also supported other energy efficiency measures such as efficient windows, insulation, PV systems and heat pumps, as well as water efficiency use. In 2021-2022 there was a new edition of this program (PAE+S2021) with support up to 85% with a maximum of 2500€. For the solar thermal system to be eligible, the energy label of the product or system must be class A+ or higher. In the case of systems with electrical electric resistance type systems or water heaters, the energy label can be A or higher.
According to Solar Heat Markets in Europe - Trends and Market Statistics 2020, SHE, December 2021, Portugal has around 1.244 million m2 of collectors, with an increase of 5.34% in 2020 related to 2019. The average installed capacity per 1000 capita is 84.7kWth whereas the European average is 73.3. The cumulative installed capacity in operation is 871 MWth.
The national energy and climate plans (NECPs) were introduced by the Regulation on the governance of the energy union and climate action (EU)2018/1999 , agreed as part of the Clean energy for all Europeans package , which was adopted in 2019.
Portugal developed its Integrated National Plan for Energy and Climate for the period 2021-2030 and its final version was approved in July 2020 (Portuguese Ministers Council Resolution nº53/2020, 10th July ).
For solar thermal PNEC indicates
“In buildings, the solar thermal should coexist with other technologies of great potential and efficiency, such as biomass boilers and heat pumps. Still, it will maintain a significant role in the preparation of hot water, and in addition to other efficient solutions, it is one of the most efficient ways for space and water heating, contributing to the increase of comfort. In the case of industry, the capacity to satisfy low / medium temperature heat needs is expected to grow substantially.”
and it predicts that solar thermal will contribute with a total of 96, 101 and 104 ktep for 2020, 2025 and 2030, respectively (see Table 9 of PNEC) to the share of renewables in Heating and Cooling, which is considered to be 41%, 45% and 49% of the total energy consumption in 2020, 2025 and 2030, respectively;
and it also considers that solar thermal can contribute to energy needs in Industry in complement to biomass and higher electrification and digitalization of the sector.
Another important document of Energy policy is the “Roadmap for Carbon Neutrality 2050 (RNC 2050) - Long-Term Strategy for Carbon Neutrality of the Portuguese Economy in 2050”  where the same role in foreseen for Solar Thermal.
 Data availableat https://globalsolaratlas.info, viewed on 11-11-20221
 Data available in “Balanço Energético – 2021” published by DGEG and available in https://www.dgeg.gov.pt/media/kmoblfag/dgeg-ben-2021.pdf , viewed on 15-11-2021.
 ADENE/INETI (2002). “Fórum Energias Renováveis em Portugal – Uma contribuição para os objetivos de política energética e Ambiental”. Eds. Hélder Gonçalves, António Joyce, Luís Silva, ISBN-972-8646-05-4. Chapter “Solar Térmico Activo” (page. 30 to 67), Prepared by Working group coordinated and edited by M. Collares Pereira, and M.J. Carvalho
 Resolution of Ministers Council nº154/2001; Água Quente Solar para Portugal, ADEME/DGE/INETI, Novembro 2001, ISBN 972-8646-02-X
 Directive 2002/91/EC of the European Parliament and of the Council of 16 December 2002 on the energy performance of buildings, withdrawn and replaced by Directive 2010/31/EU of the European Parliament and of the Council of 19 May 2010 on the energy performance of buildings, which was latter amended, as part of the Clean energy for all Europeans package, in 2018 (Directive (EU) 2018/844 of the European Parliament and of the Council of 30 May 2018 amending Directive 2010/31/EU on the energy performance of buildings and Directive 2012/27/EU on energy efficiency).