Evidencing heat network feasibility in an energy statement

Heat network feasibility planning evidence fails for one reason more than any other: the energy statement says no network was identified, without showing that anybody looked. The be clean stage of the energy hierarchy is a test you have to run and document, not a box to tick, and a case officer who cannot see the enquiries, the dates and the responses will either ask for them or refuse to accept the conclusion.

Run the search, keep the correspondence, and write the conclusion so tightly that it cannot be reopened at committee.

What the policy actually requires you to test

In London, Policy SI 3 of the London Plan 2021 sets a heating hierarchy for major development, starting with connection to a local existing or planned heat network before other options are considered. Within Heat Network Priority Areas the expectation is stronger, and proposals are also expected to be designed so that connection to a future network remains possible.

Outside London the requirement sits in local plan policy where it exists at all, and the wording varies from a hard requirement to connect where a network is available, down to a general encouragement. Read the policy rather than assuming, because the evidence you need differs. A policy requiring connection "where feasible" puts the burden on you to define and test feasibility.

There is also a legislative direction of travel worth noting. The Energy Act 2023 created the framework for heat network zoning in England, with implementation through secondary legislation and a regulator. Check the commencement position and whether any zone designation affects your site at the time you write, because this is moving.

The test is about connection, not about heating technology. An applicant who answers the be clean question by explaining why heat pumps are better has not answered it.

Identifying existing and planned networks

Cast the net wider than the obvious.

1. The relevant heat mapping for your area. In London the heat map published by the Greater London Authority identifies existing networks, priority areas and planned schemes. Elsewhere, check whether the authority or the combined authority publishes its own mapping.
2. The local plan and any energy or infrastructure supplementary planning document, which frequently name schemes that are not on any map.
3. The authority's own energy or climate team, which usually knows about schemes in development before they become public.
4. Large heat sources within a plausible distance: hospitals, universities, leisure centres, data centres, energy from waste plants and industrial sites. A planned network often starts from one of these.
5. Adjacent major development. A large consented scheme nearby may be building an energy centre with capacity to spare, and its energy statement is a public document.

Record what you searched and when. A list of sources checked, with dates, does more for the credibility of the conclusion than any amount of narrative.

Enquiries to make and what to ask for

Write to the operator or promoter and ask specific questions. Vague enquiries get vague answers, and a vague answer is worthless as evidence.

Ask whether a network exists within a stated distance of the site, and where the nearest connection point is. Ask whether there is spare thermal capacity now, and what is expected over the development programme. Ask for the basis of connection charges and the heat tariff structure, without expecting firm numbers. Ask for the technical interface requirements: flow and return temperatures, pressure, the space needed for a plate heat exchanger or hydraulic interface units, and metering arrangements. Ask what the connection agreement process is and how long it takes. And ask for a written response with a date on it.

Copy the local authority energy team into the enquiry. It costs nothing and it means the council has seen the same correspondence you will be relying on.

Where no response arrives, chase in writing and record the chasers. An unanswered enquiry with three dated follow-ups is evidence. An unanswered enquiry mentioned in passing is not.

Reading a refusal or a no capacity response

The wording of the reply determines your conclusion, and the four common answers lead to four different places.

That last row is where disputes happen. A response saying the operator will not offer terms at an acceptable price is not the same as a response saying connection is infeasible, and officers are entitled to ask what price was offered. Be ready for the question before it is asked.

Append the actual correspondence. Paraphrasing an operator's response in your own words invites a request for the original, and that request costs weeks.

Connection ready provision and what it costs

Where connection is not available now, policy generally expects the building to be capable of connecting later. That has physical consequences at design stage which are hard to retrofit.

The provision that authorities look for includes space reserved for a future plate heat exchanger or energy centre of a credible size, capped and valved pipework routed to the site boundary at a sensible point, a protected internal route from that boundary to the plant space, and space for metering. It also includes designing the internal heating system to operate at temperatures compatible with a network, because a high temperature emitter design can make later connection uneconomic even where the pipes are in place.

The cost is mostly space rather than plant. Reserving a plant room that sits empty for years is a real commercial loss, and applicants regularly try to reduce it to a cupboard. A reserved space too small for any plausible heat exchanger will be read as provision in name only.

Combustion plant brings a separate consenting problem, since gas fired engines raise emissions questions that can outweigh the carbon case, as our note on combined heat and power and air quality sets out. Heat pump alternatives carry their own consenting trail, covered in ground source heat pumps and borehole permitting.

Plant space and pipe route safeguarding

Draw the safeguarding rather than describing it. What the reviewer wants to see on the drawings is the plant space with dimensions and floor to soffit height, the door and access route wide enough to replace the largest single item of plant, ventilation provision, the pipe route from the boundary shown on every level it passes through, and the connection point on the boundary marked with a level.

Two constraints bite hardest on urban sites. Bend radii, because large diameter pre-insulated pipe cannot turn tight corners inside a basement, and the drawn route has to be physically buildable. And third party land, where the route to the nearest connection point crosses somebody else's title and needs an easement or wayleave that nobody has started negotiating.

Where the safeguarding is secured by condition or obligation, read the drafting. A condition requiring connection "if a network becomes available" with no trigger, no notice mechanism and no end date is unhelpful to both sides.

Writing the conclusion so it cannot be reopened

Structure the be clean section of the Energy Statement as a short evidential narrative in a fixed order.

State the policy requirement and quote it. List the sources searched, with dates. List the enquiries made, to whom and when, with the follow-ups. Summarise each response and cross-refer to the appended correspondence. State the conclusion in one sentence. Then set out the provision made, with drawing references. Finally, state what would change the conclusion, for example a network reaching a defined point before a defined phase.

That last element is the one most statements omit, and it is the one that closes the argument. A conclusion that names its own trigger for revisiting is much harder to attack than one presented as final.

The same discipline carries into the wider policy commitments, which usually sit in a Sustainability Statement, and into sector-specific cases such as those covered in energy statements for warehouse schemes.

This is general guidance rather than legal advice. Heat network policy and zoning are changing, so check the current policy wording and commencement position with your local planning authority before relying on any of it.

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