Every country has objectives for climate change, and public policies are implemented to achieve those commitments. This paper aims to review the different public policies used to promote the integration of photovoltaic technology into smart grids, taking the case of Portugal as reference. An analysis of previous supporting policies is performed both in Portugal and some European countries; these policies consist of feed-in tariffs, feed-in premiums, green certificates, electricity compensation, direct capital subsidies, and tax credits. The policies currently in force in Portugal no longer aim to support the technology; instead, they intend to promote it. Energy communities, local markets, and solar auctions are examples of public policies that are currently being used, not only to promote PV power but also the development of microgrids. Finally, the Portuguese solar auctions of 2019 and 2020 are analyzed and compared. It is concluded that auctions are a very effective way of expanding the installed capacity of the PV technology in the country and have more weight on promoting the technology than other promoting policies currently being used.

Positive Energy Districts (PEDs) are a promising approach to urban energy transformation, aiming to optimize local energy systems and deliver environmental, social and economic benefits. However, their effectiveness and justification for investment rely on understanding the additional value they provide (additionality) in comparison to current policies and planning methods. The additionality perspective is not used yet in current evaluations of PED demonstrations and pilots. Therefore, this paper introduces the concept of additionality in the evaluation of PEDs, focusing on the additional benefits they bring and the circumstances under which they are most effective. We discuss the additionality of PEDs in addressing the challenges of climate neutrality and energy system transformation in three European cities that are funded by the European Commission’s H2020 Programme. It should be noted that given the ongoing status of these projects, the assessment is mainly based on preliminary results, as monitoring is still ongoing and quantitative results are not yet available. The paper discusses the drivers and barriers specific to PEDs, and highlights the challenges posed by technical complexities, financing aspects and social and legal restrictions. Conclusions are drawn regarding the concept of additionality and its implications for the wider development of PEDs as a response to the challenges of climate neutrality and energy system transformation in cities. We conclude that the additionality perspective provides valuable insights into the impact and potential of PEDs for societal goals and recommend this approach for use in the final evaluation of R&I projects involving PEDs using actual monitored data on PEDs.