Heat network zoning and the connection requirement

Heat network zoning planning questions arrive on development sites in a particular order: is the site in a zone or a likely zone, does the scheme fall into a category that has to connect, and if there is no pipe in the ground yet, what has to be left in the building so it can connect later. The framework for all three sits in Part 1 of the Energy Act 2023, with the operational detail left to secondary legislation and a national zoning methodology.

As at September 2026, that secondary detail is still being brought into force in stages, so the position on any given site has to be checked rather than assumed.

What zoning introduces and who designates

Zoning identifies the areas where heat networks are expected to be the lowest cost route to decarbonised heat, using a methodology applied to heat demand density, anchor loads and available heat sources. Within a designated zone, a zoning coordinator takes on the job of delineating the zone, running the process to appoint a network developer and enforcing the requirements that apply inside it.

That is a different arrangement from the voluntary position most developers are used to, where a local plan policy encourages connection and a scheme negotiates. Inside a zone, connection becomes an obligation for specified categories of building rather than a preference.

The zones themselves are urban and demand led. A dispersed suburban scheme is unlikely to fall inside one, which is why the first question is always locational.

Connection duties inside a zone

The categories expected to carry a connection requirement are new buildings, large non-domestic buildings, communally heated residential buildings and public sector buildings, with thresholds and timescales to be set in regulations. Exemptions and appeal routes form part of the same package.

For a developer this changes the programme rather than the technology. A scheme inside a zone needs a connection agreement with the network developer, a commercial negotiation over connection charges and heat tariffs, and a construction sequence that allows the network to reach the site before occupation. None of that is unfamiliar to anyone who has dealt with a distribution network operator, and the lead times are comparable.

Do not treat the heat supply as settled because the local plan policy allows an alternative. Where a zone is designated, the zoning requirements sit alongside planning policy rather than being replaced by it.

Safeguarding a connection where no network exists yet

Most sites face the intermediate case: a zone identified or expected, but no pipe yet. Local plan policies have handled this for years through safeguarding requirements, and the usual list is short but physically demanding.

1. A plant space sized and located so that plate heat exchangers and associated pumps can be installed later, with a route for pipework to the street.
2. A valved connection point at the site boundary, at an agreed depth and location.
3. Internal distribution designed as a wet system at temperatures compatible with a future network, with the flow and return arrangement set out.
4. A heat interface unit position identified in each dwelling, with space for metering.
5. An easement or wayleave for the network developer, usually secured through the section 106 agreement.

The expensive failure is the first one. Retrofitting an energy centre into a basement designed for cycle storage is not a small change, and a scheme that has to break out a slab to bring pipework in has lost the benefit of safeguarding altogether.

Energy centre and plant room space

Plan the energy centre as a building, not as a residual. It needs floor to ceiling height for the thermal store, a door and route sized for replacing the largest component over the building's life, ventilation, drainage, acoustic separation from habitable rooms above and beside, and a delivery position for a tanker or a lorry if the design ever needs one.

Acoustic separation is where planning and design meet. An energy centre under flats generates structure borne noise from pumps, and the mitigation is a design decision about isolation and layout rather than a specification added later. The same applies to the flue arrangement where any combustion plant is retained for peak or backup duty.

Where the site will host a network energy centre serving other buildings, the space requirement grows and so does the servicing demand. Get the network developer's space requirement in writing before the layout is fixed.

Interaction with heat pump led strategies

Many schemes have already settled on air source or ground source heat pumps, and the arrival of a zone does not automatically make that strategy wrong. Ambient loop networks, sometimes called fifth generation, are themselves heat pump based, and a scheme designed around low flow temperatures is generally easier to connect than one designed around high temperature radiators.

The design decisions that protect both options are the same: low flow temperature emitters, generous pipe sizing, a wet distribution system and a plant space that can take either arrangement. Designing to 70 degree flow temperatures because it saves on radiator sizes is the decision that forecloses the choice.

Carbon accounting differs between the two, and the figures in the energy statement's Part L outputs will move depending on the assumed network carbon factor. Say which factor you have used and where it came from.

Evidence an energy statement should contain

An Energy Statement for a scheme in or near a zone should answer a short list of questions directly. Is the site within a designated or proposed zone, and on what evidence. Is there an existing or committed network within a reasonable distance, and who operates it. What connection enquiry has been made and what was the response. If connection is not proposed, why not, tested against the heating hierarchy in the relevant policy, which in London means the London Plan's energy infrastructure policy.

Where connection is deferred, set out the safeguarding measures with drawing references rather than as a written commitment. Officers have seen too many statements promising future connection with no space reserved for it.

A Sustainability Statement can carry the wider policy compliance narrative, but keep the heat network evidence in the energy statement where a consultee will look for it.

Conditions and obligations that secure connection

Two mechanisms do the work. A planning condition can require details of the safeguarding measures to be approved and implemented, which suits physical provision such as plant space, pipework routes and the connection point. A section 106 obligation suits the contractual side: a duty to enter into a connection agreement if a network becomes available within a defined period, easements for the network developer, and access rights.

Watch the trigger points. An obligation to connect before first occupation is unenforceable in practice if the network is not built, so the drafting normally needs a test of availability and a fallback. And check who carries the cost risk if the network arrives later at a higher connection charge than the appraisal assumed, because that allocation belongs in the agreement rather than in correspondence.

This is general guidance, not legal advice. Check the current zoning position and the commencement of the relevant regulations with your local planning authority before relying on it.

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