# A 100 MW battery could get a second intervention window.

> **Consultation file · England · 24 August—5 October 2026**

The government is consulting on a new route for mayoral intervention in major infrastructure projects, including standalone batteries of **100 MW or more**. It is not law yet.

## In brief

If the proposal comes into force and the mayor's strategic development strategy is adopted, a mayor could intervene after the local authority signals that it is minded to grant or refuse the application. The consultation describes a **14-day** decision window, but separately says secondary legislation will change time periods expressed in “days” and “weeks” to “working days”. The final duration and time unit must be checked in the enacted rules.

## What does the consultation propose?

The MHCLG consultation describes three stages for applications of potential strategic importance:

1. **Stage 1:** the local authority refers the application to the mayor for views.
2. **Stage 2:** when the authority is minded to grant or refuse, the consultation's 14-day example has the mayor decide whether to intervene or leave the application with the authority. The final period follows secondary legislation.
3. **Stage 3:** if the mayor calls in the application, the consultation describes a further determination stage.

![Proposed infrastructure route and London comparator](./assets/route-board.svg)

## Where does the 14-day example sit?

The consultation uses 14 days for the mayor's intervention decision after the local authority's signal. The same document announces that secondary legislation will change time periods expressed in “days” and “weeks” to “working days”. The 14 days are therefore the consultation example, not a final calendar-day rule, and they do not guarantee a second hearing. This page does not predict whether that choice would be made.

## The battery threshold has a condition

Annex A lists standalone battery storage at **100 MW or more**. This large-scale infrastructure category is described as available following adoption of a strategic development strategy (SDS). A 100 MW battery does not receive a separate route today simply because of its capacity.

## London is not the same route

Category 3J is the London comparator for developments of **50 or more homes** when the local authority is minded to refuse the application. It does not require the initial Stage 1 referral or a formal response unless refusal is intended. It is not an energy rule.

| Question | Proposed infrastructure | London / Category 3J |
| --- | --- | --- |
| Threshold | Standalone storage: 100 MW or more | Development: 50 or more homes |
| Local signal | Minded to grant or refuse | Minded to refuse |
| Window | 14-day consultation example; final unit follows secondary legislation | Separate London mechanism |

## What is known and not known?

The consultation timetable, its 14-day Stage 2 example, the announced move to working-day wording in secondary legislation, and the 100 MW threshold are known. We do not yet know the final duration and time unit, how many applications would enter the route, how many mayors would intervene, or whether the proposal will become law in this form.

## Why does it matter?

A reader can separate the capacity threshold, the SDS condition, and the mayor's intervention choice. They can use Category 3J as a London example without turning it into a battery rule. For developers, authorities, communities, and reporters, this is a reading map, not an outcome prediction.

## Source and limits

The source is [MHCLG, “Planning powers for mayors in England”](https://www.gov.uk/government/consultations/planning-powers-for-mayors-in-england/planning-powers-for-mayors-in-england), published 24 August 2026. The source text is held in a local archive and checked with SHA-256. The visible values are direct transcriptions, not estimates.

[View the evidence sheet](./data/evidence.json)

This file explains a public consultation. It is not legal guidance and does not provide instructions for avoiding referral or intervention.