Designation of Electricity Assets as Critical National Infrastructure

1. Introduction

Critical National Infrastructure (CNI) means infrastructure whose loss, disruption or destruction could seriously affect essential services, national security, the economy or public safety.

In the electricity sector, potentially critical assets include power stations, transmission networks, substations, control systems, distribution networks, interconnectors and important digital systems.

However, it is important to make one distinction. In UK law, an electricity asset is not simply given a general legal status of “CNI” by one single statute. Different legal frameworks identify critical or essential infrastructure for different purposes. For example, the NIS Regulations regulate Operators of Essential Services, while national planning policy identifies certain electricity networks as Critical National Priority (CNP) infrastructure. These are related concepts but they are not legally identical. (GOV.UK)

2. Why Electricity Assets Are Critical

Modern society depends heavily on electricity.

Electricity is necessary for:

hospitals;

communications;

transport;

water and sewage systems;

financial services;

government services;

homes and businesses; and

defence and emergency services.

A major failure of an electricity network can therefore produce consequences far beyond the energy sector.

For this reason, protecting electricity infrastructure involves both energy regulation and national-security policy.

3. Types of Electricity Assets

Electricity CNI can include several categories.

1. Generation assets

These include large power stations and renewable generation facilities whose loss could materially affect electricity supply.

2. Transmission networks

High-voltage transmission lines transport electricity over long distances.

3. Substations

Substations connect different parts of the electricity network and transform voltage.

4. Distribution networks

Distribution systems deliver electricity to final consumers.

5. Control and communication systems

Modern electricity networks depend heavily on digital systems for monitoring, balancing and controlling electricity flows.

6. Interconnectors

Interconnectors link electricity systems across borders and can contribute to system resilience and security of supply.

4. Critical National Priority and CNI Are Different

This distinction is very important for a PhD answer.

The 2025 National Policy Statement for Electricity Networks Infrastructure (EN-5) describes all power lines within its scope, including network reinforcement, upgrades and associated substations, as Critical National Priority (CNP) infrastructure. The policy applies particularly to nationally significant low-carbon infrastructure. (GOV.UK)

This is primarily a planning-policy concept.

By contrast, the Network and Information Systems Regulations 2018 (NIS Regulations) create legal duties for designated Operators of Essential Services (OES) in the energy sector. These duties concern the security and resilience of network and information systems supporting essential services. (GOV.UK)

Therefore:

CNP → planning and infrastructure-development priority

OES/CNI → security, resilience and protection

The two concepts can overlap, but they should not be treated as exactly the same legal designation.

5. NIS Regulations 2018

The NIS Regulations 2018 are particularly important for electricity infrastructure.

They apply to designated Operators of Essential Services in sectors including energy. In Great Britain, Ofgem is a joint competent authority with the relevant government department for downstream gas and electricity. (Ofgem)

An OES must take appropriate and proportionate technical and organisational measures to manage risks affecting the security of its network and information systems.

This is increasingly important because electricity infrastructure is now highly digital.

For example, a cyberattack on a control system could potentially affect physical electricity supply.

6. Cybersecurity and Physical Infrastructure

Modern electricity CNI cannot be protected only through physical security.

A transmission substation may be physically secure but still vulnerable if:

its control system is compromised;

remote access is attacked;

communications are disrupted;

malware enters operational technology; or

data used for system control is manipulated.

Ofgem's current NIS guidance requires operators to use systematic risk-management processes covering the network and information systems within their NIS scope. (Ofgem)

Thus, cybersecurity has become part of electricity infrastructure protection.

7. Planning Protection for Critical Electricity Infrastructure

The 2025 EN-5 policy is significant because it recognises the importance of electricity networks to energy security and the transition to net zero.

It states that electricity network infrastructure is essential for connecting new generation, storage and interconnection and for maintaining energy security. (GOV.UK)

The policy also states that all power lines within its scope, network reinforcement and upgrades, and associated infrastructure such as substations are treated as CNP infrastructure. (GOV.UK)

This can influence how planning authorities assess the national need for electricity infrastructure.

However, CNP status does not mean that environmental or legal requirements disappear. EN-5 expressly states that assessment principles continue to apply and that applicants must follow the mitigation hierarchy. (GOV.UK)

8. Case Law: R (on the application of Greenpeace Ltd) v Secretary of State for Business, Energy and Industrial Strategy

The courts have repeatedly considered the legality of major energy-policy and infrastructure decisions through judicial review.

Cases concerning major energy projects demonstrate that government decisions must comply with statutory duties, environmental assessment requirements and administrative-law principles.

The important point for CNI designation is that national importance does not remove the requirement for lawful decision-making.

Government may give substantial weight to energy security, but it must still comply with the relevant statutory framework.

9. Case Law: R (Finch) v Surrey County Council [2024] UKSC 20

In R (Finch) v Surrey County Council [2024] UKSC 20, the Supreme Court considered environmental impact assessment requirements for a fossil-fuel project.

The Court held that the environmental effects of a project could include relevant downstream greenhouse-gas emissions, depending on the statutory requirements. (GOV.UK)

Relevance to electricity CNI

The case demonstrates that the strategic importance of an infrastructure project does not automatically remove environmental-law requirements.

Therefore, even where electricity infrastructure is treated as nationally important or critical, decision-makers must still properly address environmental consequences.

10. Case Law: R (on the application of Spurrier) v Secretary of State for Transport

The Spurrier litigation concerning the Heathrow Airport expansion is useful for understanding large-scale infrastructure decision-making.

The courts considered whether the government had complied with statutory and environmental requirements when developing national infrastructure policy.

Relevance

The broader principle is useful for electricity CNI: national infrastructure policy must be developed and applied within the statutory framework.

The government can identify infrastructure as nationally important, but legal duties concerning environmental assessment, consultation and planning remain relevant.

11. National Security and Confidential Information

Designation as critical infrastructure can create a difficult balance between transparency and security.

Information about electricity assets may reveal:

network vulnerabilities;

control-system architecture;

security arrangements;

emergency procedures; or

locations of particularly sensitive equipment.

Publishing all such information could create security risks.

Therefore, legal systems may provide mechanisms for restricting disclosure of sensitive information while still maintaining appropriate regulatory accountability.

This is particularly important when electricity infrastructure is connected to digital systems.

12. Regulatory Enforcement

Designation or classification can create additional regulatory duties.

Ofgem has enforcement powers under the NIS framework. Its enforcement guidance explains that it can use enforcement tools where businesses fail to comply with NIS duties, including penalties and other regulatory measures. (Ofgem)

This creates a structure of:

Identification of essential service → security duties → monitoring → reporting → enforcement

The objective is not merely to punish failure but to encourage operators to maintain continuing security and resilience.

13. Electricity Assets and National Security

The concept of critical infrastructure is becoming more important because electricity systems face multiple risks:

Physical threats

Damage to substations, towers, cables or generating facilities.

Cyber threats

Attacks against operational technology and network-control systems.

Extreme weather

Flooding, storms, heat and other climate-related events.

Supply-chain risks

Dependence on particular equipment, technologies or overseas suppliers.

Systemic failure

Failure in one part of a highly interconnected network can create consequences elsewhere.

Consequently, CNI protection requires a whole-system approach.

14. Legal Importance of Designation

Designation or classification can have several consequences.

1. Higher security expectations

Operators may have to implement stronger security measures.

2. Regulatory supervision

Relevant regulators can monitor compliance.

3. Emergency planning

Critical assets may receive special consideration in resilience planning.

4. Planning priority

Where CNP policy applies, the national importance of electricity infrastructure receives significant weight in planning decisions.

5. Information protection

Sensitive infrastructure information may require additional protection.

15. Conclusion

Designation of electricity assets as Critical National Infrastructure is part of a wider UK system for protecting essential electricity services.

The legal structure is not based on one universal CNI designation. Instead, several overlapping frameworks operate together:

NIS Regulations 2018 → cybersecurity and resilience of Operators of Essential Services;

Ofgem regulation → monitoring and enforcement;

Planning Act 2008 and energy NPSs → planning of nationally significant infrastructure;

EN-5 2025 → identifies in-scope electricity networks, reinforcement, upgrades and substations as Critical National Priority infrastructure. (GOV.UK)

The central legal principle is that national importance does not eliminate ordinary legal safeguards. Electricity infrastructure may receive strong policy support because of energy security and net-zero objectives, but environmental assessment, consultation, proportionality and statutory decision-making requirements continue to apply.

For energy law, CNI designation therefore represents a shift from treating electricity assets simply as commercial infrastructure towards treating them as essential national systems requiring enhanced security, resilience, regulatory oversight and long-term protection.