1. Introduction

International investment law plays an important role in the development, financing, operation and protection of energy infrastructure. Electricity grids, pipelines, LNG terminals, power plants, renewable-energy projects, transmission systems, storage facilities, ports and cross-border interconnectors require substantial capital and often have long investment periods. Because these projects depend heavily on government licences, concessions, tariffs, subsidies, land rights and regulatory approvals, changes in government policy can materially affect their economic value.

International investment agreements (IIAs)—particularly bilateral investment treaties (BITs), free-trade agreements and the Energy Charter Treaty (ECT)—can provide foreign investors with protections against certain forms of State conduct and, in many circumstances, access to investor-State dispute settlement (ISDS).

Energy is particularly significant in investment arbitration. UNCTAD reports that approximately one-third of treaty-based ISDS cases concern energy supply and extractive industries. By the end of 2023, at least 123 ISDS proceedings had arisen in the renewable-energy sector. (Investment Policy Hub)

The central legal problem is therefore to reconcile two interests:

Protection of long-term energy infrastructure investment, and

The State's continuing right to regulate energy, environmental and climate policy.

2. Meaning of Energy Infrastructure Investment

Energy infrastructure investment covers both physical assets and associated economic rights.

Major examples include:

Electricity generation plants

Solar and wind farms

Hydroelectric facilities

Nuclear power infrastructure

Electricity transmission networks

Distribution networks

Gas pipelines

LNG terminals

Oil transportation infrastructure

Energy-storage facilities

Hydrogen infrastructure

Cross-border electricity interconnectors

Smart-grid infrastructure

Energy ports and terminals

Energy-related telecommunications and control systems.

Investment may take several legal forms:

Direct ownership of infrastructure;

Shares in an energy company;

Concession agreements;

Build-operate-transfer (BOT) arrangements;

Public-private partnerships;

Long-term power-purchase agreements;

Licences and permits;

Contractual rights;

Loans and project finance;

Intellectual property and technology rights.

Modern investment treaties may define "investment" broadly enough to encompass many of these interests.

3. Sources of International Investment Protection

A. Bilateral Investment Treaties

BITs are agreements between two States establishing protections for investors from each State investing in the territory of the other.

Typical protections include:

Fair and equitable treatment;

Full protection and security;

Protection against unlawful expropriation;

National treatment;

Most-favoured-nation treatment;

Free transfer of funds;

Protection against arbitrary or discriminatory measures;

Investor-State arbitration.

For energy infrastructure, BIT protection can be significant because projects frequently involve foreign capital and government-controlled regulatory systems.

B. Energy Charter Treaty

The Energy Charter Treaty has historically been one of the most important international investment instruments for energy projects.

Its investment provisions were designed to create a legal framework for long-term cooperation in the energy sector. Article 10, for example, contains obligations concerning stable, equitable, favourable and transparent conditions for investments and fair and equitable treatment. (ICSID)

The ECT became particularly important in renewable-energy disputes because investors used it to challenge changes to national subsidy and tariff regimes.

UNCTAD reports that the overwhelming majority of renewable-energy ISDS cases identified in its earlier dataset were brought under the ECT. (UNCTAD)

4. Fair and Equitable Treatment

Fair and equitable treatment (FET) is one of the most frequently invoked standards in energy-infrastructure arbitration.

Depending on the applicable treaty and tribunal, FET may involve considerations such as:

Protection against arbitrary governmental conduct;

Procedural fairness;

Transparency;

Consistency;

Protection of legitimate expectations;

Good faith;

Stability of the legal framework in appropriate circumstances.

However, FET does not necessarily create an absolute guarantee that energy regulations will never change.

This distinction is crucial because energy infrastructure is normally subject to evolving:

Environmental standards;

Electricity-market rules;

Tariffs;

Taxation;

Safety requirements;

Climate policy;

Grid regulations;

Licensing requirements.

UNCTAD's analysis of energy-transition disputes emphasizes the tension between investors seeking stability and States needing regulatory flexibility to change energy policies. (Investment Policy Hub)

5. Expropriation and Energy Infrastructure

Investment treaties commonly prohibit unlawful expropriation.

Expropriation can be:

Direct expropriation

This occurs when the State formally takes ownership of an investment.

Example:

A State nationalises a foreign-owned electricity transmission company without providing treaty-compliant compensation.

Indirect expropriation

This is more complicated. The State does not formally take ownership but adopts measures that allegedly deprive the investor of the substantial economic value or use of the investment.

Possible examples include:

Cancellation of a concession;

Withdrawal of a critical operating licence;

Destruction of the economic value of an energy project through regulatory measures;

Prohibition of a particular form of energy generation.

Tribunals generally have to distinguish between compensable expropriation and legitimate regulation undertaken pursuant to the State's sovereign regulatory powers.

6. Legitimate Regulatory Change

One of the most important questions in international energy investment law is:

Can a government change its energy policy after foreign investors have invested substantial capital?

The answer depends on the applicable treaty, the specific governmental commitments, the nature of the investment and the facts of the dispute.

An investor cannot automatically assume that existing:

subsidies,

feed-in tariffs,

tax incentives,

electricity prices,

licences or

regulatory arrangements

will remain unchanged for the entire life of an infrastructure project.

At the same time, exceptionally specific governmental assurances or contractual commitments may create stronger arguments for investor protection.

This issue has produced extensive litigation involving renewable-energy incentives.

7. Renewable Energy and Investment Protection

Renewable-energy infrastructure provides an important example of the relationship between investment law and energy regulation.

Governments have often used:

Feed-in tariffs;

Renewable-energy certificates;

Tax incentives;

Guaranteed purchase prices;

Subsidies;

Priority grid access.

These mechanisms encourage private investment.

However, governments may later modify them because of:

Fiscal pressures;

Falling technology costs;

Electricity-market reform;

Consumer-price concerns;

Changes in energy policy;

Overcompensation;

Climate-policy restructuring.

These modifications have generated numerous investment disputes.

UNCTAD recorded at least 129 renewable-energy ISDS proceedings by the end of 2024, many involving changes to renewable-energy incentive schemes. (UNCTAD)

8. Important Case Law

A. Charanne Construction Ltd and Construction Investments v Spain

The Charanne v Spain arbitration concerned investments in Spain's photovoltaic sector and subsequent changes to the regulatory framework.

The case is important because it illustrates that an investor's expectation of regulatory stability is not necessarily equivalent to an absolute right to preservation of the existing regulatory regime.

The dispute became part of the broader Spanish renewable-energy arbitration litigation concerning changes to support mechanisms.

Legal significance

The case illustrates the distinction between:

legitimate regulatory evolution; and

treaty-inconsistent interference with protected investment expectations.

9. Eiser Infrastructure v Spain

Eiser Infrastructure Limited and Energía Solar Luxembourg S.à r.l. v Kingdom of Spain, ICSID Case No. ARB/13/36, involved investments in Spanish renewable-energy facilities.

The investors challenged reforms affecting the economic regime applicable to renewable-energy projects.

The tribunal found a breach of the ECT's fair-and-equitable-treatment obligation and awarded compensation.

The case became one of the prominent examples of investor protection being applied to changes affecting renewable-energy infrastructure.

Its broader importance lies in demonstrating that investment treaties can constrain the manner in which governments restructure energy-support mechanisms.

10. Antin Infrastructure Services v Spain

Antin Infrastructure Services Luxembourg S.à r.l. and Antin Energia Termosolar B.V. v Spain concerned investments in concentrated solar-power infrastructure.

The investors challenged changes to Spain's renewable-energy framework.

The tribunal found violations of the ECT's fair-and-equitable-treatment standard and awarded compensation.

The case demonstrates the importance of analysing:

Government representations;

The regulatory framework existing when investment was made;

The characteristics of the particular investment;

The extent of regulatory change;

The investor's legitimate expectations.

11. Hydro Energy 1 and Hydroxana v Spain

This case involved renewable-energy investments affected by Spanish energy reforms.

The tribunal awarded approximately €30.9 million, finding a violation of fair and equitable treatment. (Investment Policy Hub)

The case is especially useful because it demonstrates that investment tribunals can distinguish between the different treaty claims rather than automatically treating regulatory change as expropriation.

The case involved allegations including:

Indirect expropriation;

Fair and equitable treatment;

Full protection and security;

Arbitrary or discriminatory measures.

The tribunal ultimately found a breach of FET. (Investment Policy Hub)

12. Renergy v Spain

RENERGY S.à r.l. v Spain concerned investments in two thermosolar plants.

The investor challenged Spanish energy reforms under the ECT.

The tribunal awarded approximately €32.9 million and found a breach of fair and equitable treatment. The award was subsequently upheld in ICSID annulment proceedings in 2024. (Investment Policy Hub)

Importance

The case demonstrates the continuing significance of:

Regulatory expectations;

Energy-sector reforms;

Treaty standards;

Compensation;

Post-award review.

13. BayWa r.e. v Spain

BayWa r.e. Renewable Energy GmbH and BayWa r.e. Asset Holding GmbH v Kingdom of Spain, ICSID Case No. ARB/15/16, involved investments in Spanish solar-energy infrastructure.

The dispute arose from changes to Spain's renewable-energy regulatory regime, including reductions in subsidies and changes affecting electricity generators. (Investment Policy Hub)

The case illustrates how investors can invoke treaty protection when regulatory reforms materially affect the economics of infrastructure investments.

14. Cube Infrastructure v Spain

In Cube Infrastructure Fund SICAV and others v Spain, the investors held a majority shareholding in a Spanish renewable-energy company.

The dispute concerned Spanish energy reforms, including a tax affecting electricity generators and reductions in renewable-energy support. (Investment Policy Hub)

This demonstrates that investment protection can extend beyond direct ownership of physical infrastructure: shareholdings in energy companies can themselves constitute protected investments.

15. E.ON v Spain

E.ON SE and others v Spain involved investments in solar, wind and mini-hydro electricity facilities.

The dispute concerned Spanish reforms affecting renewable-energy investments, including a 7% tax on generators' revenues and reductions in subsidies. (Investment Policy Hub)

This case illustrates the breadth of infrastructure investments potentially affected by changes in energy policy.

16. I.C.W. v Czech Republic

I.C.W. v Czech Republic concerned amendments to incentives applicable to renewable-energy investments, including a levy on electricity generated by solar installations.

The UNCITRAL tribunal, administered by the Permanent Court of Arbitration, ultimately decided in favour of the State in its 2019 award. (Investment Policy Hub)

Significance

The case illustrates that not every adverse change to renewable-energy economics constitutes an international-law violation.

This is important because investment protection does not mean that investors are guaranteed a particular level of profitability.

17. Enel v Türkiye

Enel, S.p.A. v Republic of Türkiye, ICSID Case No. ARB/21/61, concerns an investment in a renewable-energy generation enterprise.

The dispute arose following the energy regulator's alleged cancellation of a pre-licence for a solar power plant. (Investment Policy Hub)

The case demonstrates the importance of licensing and regulatory approvals in energy infrastructure investment.

Energy projects are particularly dependent on State authorisations, meaning that cancellation, non-renewal or modification of licences can become significant investment-law issues.

18. Infrastructure Concessions and PPPs

International investment law is particularly important for public-private partnerships (PPPs).

Energy infrastructure is often constructed through arrangements where:

The State retains ultimate regulatory authority;

A private investor finances and constructs infrastructure;

The investor operates it for a defined period;

Revenue is generated through tariffs or contractual payments;

The asset may eventually return to the State.

Potential disputes may involve:

Termination of concessions;

Changes in tariffs;

Failure to make contractual payments;

Revocation of licences;

Regulatory interference;

Changes in taxation;

Renegotiation of infrastructure agreements.

UNCTAD notes that PPP-related investment disputes commonly involve alleged unjustified termination or suspension of concessions, contractual breaches and legislative changes affecting project profitability. (UNCTAD)

19. Energy Infrastructure and Political Risk

Energy projects are particularly exposed to political and regulatory risk because they usually have:

High initial capital expenditure;

Long payback periods;

Significant dependence on government approvals;

Physical immobility;

Strong public-interest dimensions;

Exposure to environmental regulation;

Dependence on electricity or fuel markets.

Consequently, investors may seek treaty protection against extreme forms of political interference.

However, States retain substantial authority to regulate matters such as:

Public health;

Environmental protection;

Energy security;

Consumer protection;

Electricity reliability;

Climate change;

Public safety.

20. Climate Change and Investment Law

Climate change has introduced a new dimension to energy investment law.

Governments increasingly need to:

Reduce fossil-fuel consumption;

Close coal-fired power plants;

Increase renewable generation;

Develop transmission infrastructure;

Expand energy storage;

Regulate methane emissions;

Introduce carbon pricing;

Electrify transport and industry.

These policies can affect existing energy investments.

UNCTAD identifies both fossil-fuel and renewable-energy disputes as important components of the investment-law challenges associated with the energy transition. (UNCTAD)

For example, RWE v Netherlands and Uniper v Netherlands arose from legislation requiring the eventual cessation of coal-fired electricity generation. Both proceedings were ultimately discontinued. (UNCTAD)

The cases illustrate the interaction between investment protection and governmental climate policy.

21. Regulatory Space and the Police Powers Doctrine

International investment law generally recognises that States do not surrender their sovereign regulatory authority merely by accepting foreign investment.

The police powers doctrine helps distinguish legitimate public-interest regulation from compensable expropriation.

Relevant regulatory objectives may include:

Environmental protection;

Climate policy;

Public health;

Energy security;

Electricity reliability;

Consumer protection.

The precise scope of this doctrine depends upon the applicable treaty and arbitral jurisprudence.

Modern investment treaties increasingly attempt to clarify the relationship between investor protection and the State's right to regulate.

22. Compensation

Where a tribunal establishes a treaty breach, compensation may be calculated using various approaches.

Potential methodologies include:

Discounted Cash Flow

The tribunal estimates future revenues and expenses and discounts them to present value.

Comparable transactions

The value of comparable infrastructure investments may be considered.

Book value

Historical investment costs may provide a reference point.

Market value

Where a reliable market exists, the asset's market value may be relevant.

Energy infrastructure valuation can be particularly difficult because infrastructure projects often have:

Long operating lives;

Regulated tariffs;

Uncertain electricity prices;

Government subsidies;

Technological risks;

Changing environmental requirements.

23. Importance of Contractual Protection

International investment law should not be confused with ordinary contract law.

An energy investor may simultaneously have:

A domestic-law concession;

A power-purchase agreement;

A financing agreement;

A BIT or multilateral treaty;

Access to domestic courts;

Potential access to international arbitration.

A breach of contract does not automatically constitute a breach of an investment treaty.

The investor generally has to establish that the State's conduct violates a treaty obligation or that the relevant treaty contains an umbrella clause capable of elevating certain contractual commitments.

24. International Investment Law and Energy Security

Energy infrastructure has strategic importance because electricity and fuel systems are essential to national security and economic activity.

Investment law therefore intersects with:

Energy security;

Foreign investment screening;

Nationalisation;

Critical infrastructure protection;

Sanctions;

Supply-chain security;

Cross-border energy projects.

States may impose restrictions on foreign ownership of strategically important infrastructure.

Such measures can potentially raise investment-law questions concerning:

Discrimination;

Expropriation;

Fair treatment;

Legitimate public-interest regulation.

25. Cross-Border Energy Infrastructure

Investment law is also relevant to:

International electricity interconnectors;

Cross-border pipelines;

LNG infrastructure;

Transnational transmission systems;

Hydrogen pipelines;

Offshore electricity networks.

These projects may involve multiple legal regimes simultaneously:

Investment treaty + host-State law + concession agreement + energy regulation + environmental law + international arbitration law.

This makes dispute prevention particularly important.

26. Key Legal Principles Emerging from the Case Law

The energy-infrastructure cases demonstrate several broad principles.

1. Investment protection is not absolute

Foreign investors receive treaty protections, but States generally retain regulatory authority.

2. Regulatory stability matters

Where governments make specific and sufficiently clear commitments, abrupt regulatory changes can create treaty risks.

3. General legislation is different from specific promises

A general regulatory framework does not necessarily constitute a permanent guarantee of unchanged economic conditions.

4. Energy regulation creates special risks

Energy infrastructure is unusually dependent on licences, tariffs, subsidies and government policy.

5. Renewable-energy disputes are particularly significant

Changes to feed-in tariffs and other incentive schemes have generated a large body of international arbitration.

6. Climate policy creates new legal tensions

Governments may need to phase out carbon-intensive infrastructure while simultaneously respecting existing investment commitments.

7. Treaty drafting is increasingly important

Modern treaties can expressly preserve the State's right to regulate for environmental and climate objectives.

27. Significance for Developing Countries

For developing States, international investment law can help attract capital for:

Electricity generation;

Transmission;

Renewable energy;

Rural electrification;

Grid modernization;

Energy storage;

Gas infrastructure;

Hydrogen infrastructure.

However, poorly designed investment commitments can increase the financial exposure of governments when energy policy changes.

Therefore, governments increasingly need to design investment treaties and infrastructure contracts that provide:

Regulatory flexibility;

Clear environmental exceptions;

Transparent tariff mechanisms;

Appropriate dispute-resolution provisions;

Clear definitions of protected investments;

Anti-abuse provisions;

Provisions dealing with climate transition.

28. Conclusion

International investment law is a major component of the legal architecture governing energy infrastructure investment. It provides foreign investors with protections against certain forms of State interference while preserving, subject to the particular treaty, considerable governmental authority to regulate energy markets.

The renewable-energy disputes involving Spain, together with cases such as Eiser, Antin, Hydro Energy 1 and Hydroxana, Renergy, BayWa, Cube Infrastructure, E.ON and I.C.W. v Czech Republic, demonstrate the central tension between investment protection and regulatory change. (Investment Policy Hub)

The contemporary challenge is particularly significant because the energy transition requires governments to transform infrastructure and energy markets while investors require sufficient legal certainty to commit capital over decades. UNCTAD's recent work identifies this tension as a central issue in reforming the investment-treaty regime for the energy transition. (Investment Policy Hub)

Accordingly, the future of international investment law in energy infrastructure is likely to depend on achieving a workable balance between investment security, sovereign regulatory space, energy security, infrastructure development and climate-transition objectives.