What earthing do business EV chargers need with PME or TT?

Your electrical designer must assess the supply earthing and the charging location before choosing protection. PME can be used with suitable protective measures; TT is an alternative with its own separation problems. The IET explains the options under Section 722, rather than requiring an earth rod for every charger [S1]. Checked October 2026.

Last checked 16 October 2026

What are the EV charging earthing requirements at your site?

Start with your electrical installation, rather than a charger’s sales description. Earthing provides a protective connection for accessible conductive equipment. PME means protective multiple earthing. TT describes an arrangement using a local earthing connection for the installation’s protective earth. The distinction affects the protection your designer selects for outdoor charging. The IET explains that PME is not automatically excluded for EV charging, but protective conditions apply [S1].

This guide helps you commission that assessment. It is not an installation design or instructions for changing your supply. Read the Section 722 guide alongside the quotation. Ask the designer to identify which edition and amendments of the wiring standard apply to the proposed work.

Give the surveyor the proposed bay layout, intake photographs and any existing electrical records. Show where customers walk and where delivery vehicles park. Ask for a marked-up plan explaining the chosen approach before you reserve a trench route or order charging pedestals. A drawing makes assumptions easier to challenge than a line saying only “earthing included”.

Can EV chargers use PME earthing safely?

A PEN conductor combines protective earth and neutral functions. If it breaks upstream, accessible metalwork connected through the supply earth can become hazardous. The IET identifies this open PEN risk and discusses open PEN detection devices as a protective option. It also warns that these devices have limitations [S2].

For procurement, ask the designer to name the protective method and show why it suits the actual supply. Request the equipment instructions and the scope of the protection: which circuits and connectors does it cover? Treat “protection built in” as a prompt for evidence rather than the end of the discussion.

Do not assume that a device selected for another site can be copied into your design. The IET’s detailed guidance identifies limitations concerning supply phases and operation alongside equipment capable of island mode [S3]. Ask specifically about planned solar and battery additions, even if you are buying chargers first.

Is TT earthing a simpler option than PME?

TT can be an option, but the earth rod and surrounding installation need assessment. The IET highlights problems with separation from other earthing arrangements and nearby metalwork, including equipment outside your own boundary [S2]. Converting the charging area to TT is therefore a design choice, not a universal shortcut.

Ask the contractor to show how excavation, service detection, testing and reinstatement are priced. If the survey changes the approach, request the revised scope before authorising work. Avoid comparing an equipment-only price with a quotation that includes the necessary site investigation.

For a leased car park, show the proposed earth rod and cable route to the landlord as part of the consent request. Ask your solicitor to check any access or reinstatement obligations in the agreement. Keep the technical design decision with the electrical designer.

Why does nearby metalwork matter?

The IET’s guidance identifies both simultaneous contact and underground separation as issues for separate earthing arrangements. an earth rod placed too close to PME-connected buried metalwork may undermine the intended separation [S3]. Your designer needs to look beyond the charging pedestal.

During the survey, point out lighting columns, powered gates, building steelwork, neighbouring charging bays and anything that is due to be installed later. Do not decide yourself which items need bonding or separation. Ask the designer to record the assessment and any restrictions that affect the bay layout.

If parking spaces move during a later resurfacing project, use that record to trigger a review. Include the electrical layout in the site information given to future contractors. This is a practical way to stop a later landscaping or lighting project overlooking assumptions made in the original charging design.

Does open PEN protection replace an RCD?

The protective functions are different. A residual current device, or RCD, detects residual current associated with certain faults. The IET explains charging-point RCD requirements and notes that final circuits may also need RCD protection for other reasons, including a TT arrangement [S4]. An open PEN feature does not answer all the questions about circuit protection.

Ask for a protection schedule rather than trying to select an RCD type from a brochure. It should identify what is inside the charging equipment and what the contractor adds upstream. Use the RCD explainer to prepare questions, then have the designer confirm the selection for your equipment.

What should the earthing quotation and handover include?

Request a named person responsible for design, a clear survey scope and a list of unresolved supply questions. Ask whether the contractor needs confirmation from your distribution network operator, or DNO: the company responsible for the local electricity network. Keep that response with the design records.

Before accepting handover, request the drawings, equipment instructions, inspection and test records, and a clear fault-reporting route. The IET discusses testing of protection associated with charging points [S1]. Our certificate guide helps you organise the paperwork. Ask who will review the arrangement when you extend the installation or change equipment.

What should you do next?

Prepare your intake records and bay plan using the site survey guide, then get matched with an installer that covers your area. Request a site-specific earthing assessment with the charging quotation.

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