Background
Following the 2007 introduction of generous feed-in tariffs for renewable energy, Spain attracted billions of euros of foreign investment into solar PV and concentrated solar power. Beginning in 2010, the government progressively reduced and then retroactively eliminated those tariffs through a series of measures culminating in the 2013–2014 reforms. Foreign investors filed under the Energy Charter Treaty (ECT) seeking compensation for the impairment of their investments.
Caseload
By 2025, more than 50 ECT cases had been filed against Spain. Roughly two-thirds of those decided on the merits resulted in awards for the claimants, though quantum and damages methodologies have varied considerably. The Spanish caseload is the single largest concentration of treaty disputes against any state in history.
For broader context, see our ICSID Caseload Trends 2026.
Substantive standards
Most awards turn on the Fair and Equitable Treatment standard, specifically the legitimate-expectations element. Tribunals have generally found that Spain's specific assurances and the legal framework in place at the time of investment created investment-backed expectations that the post-2010 measures breached. A minority of tribunals have given greater weight to Spain's right to regulate, particularly where measures were enacted in good faith to address macroeconomic pressure.
EU intra-EU objections
Spain has consistently raised the EU intra-EU jurisdictional objection following the CJEU's Achmea and Komstroy rulings. Tribunals have largely rejected this objection on the basis of ICSID Article 26's exclusion of national-law remedies, but enforcement of awards within the EU has become significantly harder.
Looking ahead
The Spanish caseload is winding down as the pre-modernisation ECT window closes, but enforcement battles will continue for years. For investors and counsel, Spain remains the canonical case study in regulatory reversal and treaty-based remedy.