High Voltage (HV) Connections and Substations

When Do You Need an HV Connection?

Most homes and small commercial units run on a low voltage (LV) supply. But once a site's power demand grows beyond what LV can deliver, usually above around 500 kVA, it needs a high voltage connection with its own substation to step the voltage down to a usable level. You typically need an HV connection when your project involves:

• A large commercial or industrial development
• A data centre or high-density computing facility
• A battery energy storage system (BESS) or renewable generation site
• A large multi-plot or high-rise residential scheme
• EV charging hubs with rapid or ultra-rapid chargers at scale
• Any site whose total load exceeds the capacity of a low voltage supply

If you are unsure whether your project needs HV or LV, we confirm this at the feasibility stage by assessing your total load against the available network capacity.

HV Connection Services

• HV connection design to DNO and IDNO adoptable standards
• Point of connection applications and all network operator liaison
• Customer substation design and installation, including 11kV
• HV cable laying, jointing and termination
• Transformer supply and installation to step HV down to LV
• Switchgear, protection and metering for the HV network
• Private HV network design for large sites and campuses
• Testing, commissioning, energisation and adoption

Voltage Tiers Explained

The UK distribution network operates at several voltage levels. Which one your project connects at depends on how much power it needs.

Air Utilities is NERS accredited to design and construct HV connections and substation installations at 11kV and 20kV. Where a project requires EHV capability at 33kV or 132kV, such as a hyperscale data centre or a grid-scale battery site, we deliver it through our network of accredited specialist partners, so the work is always carried out by a provider fully qualified for that voltage.

HV Connections for Data Centres and Battery Storage

Two sectors are driving unprecedented demand for high-capacity power connections: data centres and battery energy storage.

Data centres, particularly those supporting AI and high-density computing, need far more power than a standard HV supply can provide, and they need it to be resilient. Larger facilities often require EHV connections with dual-feed arrangements, two independent circuits from the grid connection point, so that if one circuit fails, the second maintains the load with no downtime. Battery energy storage systems (BESS) and renewable generation sites likewise need HV or EHV connections to export and import power at scale, and grid capacity is now a critical constraint on these projects.

We assess capacity and resilience requirements early, because on these schemes the grid connection, not the building, is often the longest lead item on the whole programme.

Customer Substations

Any HV connection needs a substation to transform the high voltage supply down to a usable low voltage. We design and install customer substations to network-adoptable standards, including:

• Packaged and containerised substations for faster installation
• 11kV / 400V transformers sized to your load
• HV switchgear and protection to network specifications
• Metering at the HV interface

The substation is one of the largest single elements of an HV connection, both in cost and lead time, so getting its specification and location right early is essential. We design it into the connection from the feasibility stage rather than treating it as an afterthought.

Why Use Air Utilities for HV Connections

• NERS accredited for HV design and substation installation at 11kV and 20kV
• Partner network for EHV, so 33kV and 132kV projects are covered by fully qualified specialists under one point of contact
• Whole-project delivery, from feasibility and design through construction to energisation and adoption
• Multi-utility capability, so HV power can be delivered alongside gas, water and EV infrastructure on the same site
• Adoptable by the network, designed to DNO and IDNO standards from day one

How Long Does an HV Connection Take?

HV connections take longer than LV connections because of the substation, the volume of network liaison, and the design approvals involved. As a general industry guide, an HV connection with a new substation commonly runs to several months from engagement to energisation, and EHV connections for data centres or grid-scale sites can take considerably longer, since grid capacity and network works dominate the timeline. This is exactly why the grid connection should be one of the first things addressed on a large project, not one of the last. We start feasibility and point of connection applications early so the connection does not become the bottleneck on your programme.

Our HV Connection Process

1. 1

   Feasibility and load assessment

   We confirm your total load, whether HV is required, and the available network capacity.

2. 2

   Point of connection

   We apply to the network operator for the point of connection and any budget estimate.

3. 3

   Design

   We design the HV connection and substation to DNO or IDNO adoptable standards.

4. 4

   Construction

   Our accredited teams install the HV cabling, substation, transformer and switchgear (11kV and 20kV directly; 33kV and above through accredited partners).

5. 5

   Commissioning, energisation and adoption

   We test and commission the network, the operator energises and adopts it, and you receive full documentation on handover.

Frequently Asked Questions