Key data
| Regulation | Ruling of April 29, 2026, Third Chamber of the Supreme Court, administrative contentious appeal 671/2024 |
|---|---|
| Annulled norm | Royal Decree 662/2024, of July 9, on floating photovoltaic plants in hydraulic public domain reservoirs |
| Norm modified by RD 662/2024 | Regulation of Hydraulic Public Domain (Royal Decree 849/1986, of April 11) |
| Publication of the ruling | June 3, 2026 |
| Entry into force | June 3, 2026 |
| Appellant | Autonomous Community of Aragón (Legal Counsel of the Community of Aragón) |
| Defendant | General State Administration |
| Costs | Imposed on the General State Administration |
| Affected parties | Floating solar energy promoters, hydraulic administrations, autonomous communities |
| Category | Energy |
Floating solar energy promoters in reservoirs managed by the General State Administration face a scenario of total legal uncertainty as of June 3, 2026. The Third Chamber of the Supreme Court, in a ruling issued on April 29, 2026 and published on June 3, has upheld the appeal filed by the Autonomous Community of Aragón and has declared the nullity of Royal Decree 662/2024, which was the only regulatory instrument governing the installation of floating photovoltaic plants in hydraulic public domain reservoirs of inter-community basins.
The basis for the annulment is jurisdictional: the Supreme Court has sided with Aragón in its argument that the State invaded autonomous competencies in energy and water matters by approving that decree without respecting the constitutional distribution of competencies between the State and the autonomous communities.
What does this ruling establish?
The Supreme Court ruling has three immediate and concrete legal effects:
- Nullity of Royal Decree 662/2024: The decree is expelled from the legal system as if it had never existed. This is not a partial annulment or temporary suspension.
- Elimination of modifications to the Hydraulic Public Domain Regulation: RD 662/2024 also modified the Regulation approved by Royal Decree 849/1986, of April 11. Upon annulment of the decree, those modifications are also without effect.
- Costs imposed on the State: The General State Administration must assume the costs of the proceedings, reflecting the strength of the ruling in favor of Aragón.
The underlying reason is the distribution of competencies between the State and the autonomous communities in energy and water matters. The Supreme Court has considered that the central Government overstepped its authority by regulating through decree an area that affects autonomous competencies without the appropriate procedure.
As a direct consequence, the Government must develop new regulations that respect autonomous competencies if it wishes to regulate this sector again.
Economic and operational impact
The economic impact of this ruling is not measured in fines or new fees: it is measured in stalled projects, investments at risk, and missed deadlines.
- Projects in processing: Any authorization file initiated under RD 662/2024 now lacks legal basis. Authorizations granted under that decree may be subject to challenge.
- Committed investments: Promoters who have incurred expenses for engineering, environmental impact studies, administrative fees, or contractual commitments under the umbrella of the annulled decree face the possibility that those investments will not generate returns in the short term.
- Indefinite regulatory vacuum: There is no legal deadline for the Government to approve new regulations. The sector remains in suspension until a new framework is published that respects autonomous competencies.
- Risk of claims: Affected promoters could explore actions for State patrimonial liability for damages resulting from the application of a norm declared null.
Who does it affect?
- Floating solar energy promoters and companies with projects in reservoirs of inter-community hydrographic basins managed by the General State Administration (Ebro, Duero, Tajo, Guadiana, Guadalquivir, Segura, Júcar, Miño-Sil, Cantabrian and Galicia Coast Hydrographic Confederations).
- Investors and funds with participation in floating photovoltaic projects in Spanish state reservoirs.
- Hydraulic administrations (Hydrographic Confederations) that processed authorizations under the annulled decree.
- Autonomous communities with reservoirs in their territory affected by inter-community basins, especially Aragón, which promoted the appeal.
- Legal advisors and energy consultants advising promoters with ongoing projects.
- Engineering and construction companies with contracts linked to floating photovoltaic projects in state reservoirs.
Practical example
A renewable energy promotion company had initiated in 2024 the processing of a floating photovoltaic plant in a reservoir managed by the Ebro Hydrographic Confederation, relying on the procedure established by Royal Decree 662/2024. It had commissioned environmental impact studies, submitted the authorization request to the Confederation, and committed significant economic resources to the project.
As of June 3, 2026, the legal framework supporting that file has disappeared. The Hydrographic Confederation cannot continue processing the authorization under a norm declared null. The promotion company must:
- Halt any progress in processing until new regulations exist.
- Evaluate with its legal counsel whether the authorization, if granted, is subject to challenge by third parties.
- Analyze whether it has the right to claim from the State damages and losses resulting from having acted in good faith under a norm that the State itself approved and that has been declared null.
What should companies do now?
- Review the legal status of each project: Identify whether the authorization file was initiated under RD 662/2024 and at what stage it is. A project with authorization already granted has different risk than one in processing.
- Consult with legal counsel specialized in energy and administrative law: Nullity has retroactive effects. It is essential to evaluate the legal soundness of each specific situation before making investment decisions.
- Communicate with the corresponding Hydrographic Confederation: Request information on how the ruling affects files in processing and what criteria the hydraulic administration will adopt from now on.
- Document all expenses and investments made: If a claim for State patrimonial liability is contemplated, it will be necessary to prove the economic damages suffered as a result of having acted under a norm declared null.
- Monitor the publication of new regulations: The Government must approve a new regulatory framework that respects autonomous competencies. Staying aware of drafts and public consultations will allow anticipation and participation in the process.
- Evaluate alternative projects: While new regulations do not exist, assess whether projects can be reoriented to reservoirs of autonomous ownership, where regulatory competency corresponds to each autonomous community.
Frequently asked questions
What happens to authorizations already granted under Royal Decree 662/2024?
The nullity declared by the Supreme Court has retroactive effects. Authorizations granted under RD 662/2024 may be subject to challenge for lacking valid legal basis. Each case must be analyzed individually with specialized legal counsel, as principles of legitimate confidence and legal certainty may apply to protect consolidated situations.
When will there be new regulations for floating solar plants in reservoirs?
There is no established legal deadline. The ruling requires the Government to develop new regulations that respect autonomous competencies in energy and water matters, but does not set a timeline. The sector must monitor regulatory initiatives from the Ministry for Ecological Transition and Demographic Challenge.
Can a promoter claim damages from the State for having invested under RD 662/2024?
Yes, it is a path that can be explored. State patrimonial liability for legislative or regulatory acts declared null is recognized in the Spanish legal system. The promoter must prove actual damage, causal relationship with the application of the annulled decree, and that it acted in good faith. It is recommended to document all expenses incurred and consult with a specialized lawyer.
Does this ruling affect reservoirs of autonomous ownership?
Not directly. RD 662/2024 exclusively regulated floating photovoltaic plants in reservoirs located in the hydraulic public domain of hydrographic basins whose management corresponds to the General State Administration (inter-community basins). Reservoirs of autonomous ownership are governed by the regulations of each autonomous community, which are not affected by this ruling.
Why did the Supreme Court annul the decree? What was the reason?
The reason was jurisdictional. The Autonomous Community of Aragón argued that the State invaded autonomous competencies in energy and water matters by approving RD 662/2024 without respecting the constitutional distribution of competencies. The Supreme Court upheld that argument and declared the decree null and void. Costs were imposed on the General State Administration, reflecting the strength of the ruling.
Official source
Consult complete regulations in official source
Notice: This article is for informational purposes only and does not constitute legal advice. For specific decisions, consult a qualified professional. Source: https://www.boe.es/diario_boe/txt.php?id=BOE-A-2026-11850