DCM Energy v. Spain is an investor-state arbitration case brought by German investors against the Kingdom of Spain under the Energy Charter Treaty (ECT). The dispute arises from Spain's significant reforms to its renewable energy regulatory framework. The Claimants, DCM Energy GmbH & Co. Solar 1 KG, C-Sun e.K., and Mr. Heinz-Jürgen Hinderer, invested in photovoltaic (PV) solar plants in Spain, relying on a legal framework, primarily Royal Decree 661/2007 (the "Special Regime"), which offered a stable feed-in tariff (FiT) system. Beginning around 2010, Spain radically altered this regime, substantially reducing the revenues of existing solar plants. The Claimants initiated ICSID arbitration in 2017, alleging that Spain's reforms breached the Fair and Equitable Treatment (FET) standard, constituted an unlawful indirect expropriation, and breached the treaty's umbrella clause. In its first decision on September 30, 2024, the Tribunal, chaired by Karl-Heinz Böckstiegel, dismissed Spain's jurisdictional objections, including the intra-EU objection based on the *Achmea* judgment. On the merits, the Tribunal found that Spain had breached its FET obligation under ECT Article 10(1) by frustrating the Claimants' legitimate expectations of a stable regulatory framework, but dismissed the expropriation and umbrella clause claims. This finding on liability was not unanimous; arbitrator Pierre-Marie Dupuy issued a dissenting opinion, arguing that the majority had incorrectly interpreted the scope of the FET standard and that Spain's regulatory changes were a legitimate and foreseeable exercise of its sovereign powers in response to changing economic circumstances, and therefore did not violate the Claimants' legitimate expectations. Following this decision on liability, the Tribunal proceeded to the quantum phase. The Claimants, supported by their expert from FTI Consulting, argued for damages based on a discounted cash flow (DCF) analysis to determine the fair market value of their investment 'but for' the breach. Spain, with its expert from Compass Lexecon, challenged this valuation, proposing alternative calculations. The Tribunal adopted the DCF methodology as the appropriate standard for compensation. In its final Award of September 8, 2025, the Tribunal ordered Spain to pay the Claimants €28.19 million in damages. This figure was reached after the Tribunal made its own adjustments to the parties' models, particularly concerning assumptions about future electricity prices and the appropriate discount rate, to reflect the value of the investment had the infringing measures not been enacted. The Tribunal also awarded pre-award and post-award interest on the principal sum to ensure full reparation for the harm suffered. The costs of the arbitration were split equally between the parties, with each party bearing its own legal fees.