The Be Clean stage: heat networks and connection evidence

The Be Clean stage of an energy statement is where most London schemes lose time, because it is the only stage that depends on a third party answering a letter. Be Lean is a design exercise you control. Be Green is a specification you choose. Be Clean asks whether your scheme can connect to a heat network, and answering that properly means writing to an operator, waiting, and documenting what came back.

Authorities now expect that correspondence as evidence rather than a statement that connection was considered and found unfeasible. An energy statement that asserts no network exists, without showing the enquiry, gets a request for further information at validation or shortly after.

What Be Clean requires of a scheme

The energy hierarchy in the London Plan runs Be Lean, Be Clean, Be Green, Be Seen. The second stage is about supplying heat efficiently, and the plan sets a heat source hierarchy within it.

The order of preference starts with connection to an existing or planned local heat network. Where that is not available, the preference moves to zero-emission or local secondary heat sources, used with a heat pump where required, then to lower temperature heating systems, and only then to combined heat and power or to gas boilers meeting low emission standards.

Two points follow for a developer. First, the gas boiler option sits at the bottom of the list, so a scheme proposing it has to show that everything above it was examined. Second, the hierarchy is about the heat source, not about the distribution system, and major development in a heat network priority area is separately expected to use a communal low-temperature heating system so that it can connect later even if it cannot now.

Checking for an existing or planned network

Start with the published heat mapping for the area, which identifies heat network priority areas and existing networks. Record the check with a date and a screenshot reference in the appendices, because the mapping is updated and an officer checking two years later will see something different.

Then look beyond the map. Networks under development do not always appear on it, and the sources worth checking are the local authority's own energy team, any adopted local plan policy identifying a network or an energy centre, and large heat sources near the site such as a hospital, a university campus, a data centre or an energy from waste plant. A nearby heat source with recoverable output can change the answer entirely, and the feasibility of data centre heat recovery into a district network is now a live question in several boroughs.

The regulatory position is also changing. The Energy Act 2023 created the framework for heat network zoning in England, with a regulator and powers to require connection within designated zones. As at October 2026 the detailed zoning arrangements are being introduced in stages, so check the current position rather than relying on a precedent from an earlier scheme.

Evidence of a connection enquiry

This is the part to get right, and it is largely administrative.

Write to the operator or the authority's energy team with enough information for them to answer: site address and boundary, proposed uses and floor areas, estimated annual heat demand in megawatt hours, estimated peak heat load in kilowatts, and the programme including the date heat would first be required. An enquiry without a demand estimate will not get a useful reply.

Then keep a log. The appendix should contain the enquiry letter or email with its date, any acknowledgement, the substantive response, and any follow-up. Where there has been no response, show the chasing correspondence and the dates.

The response you are looking for addresses four things: whether a network exists or is planned within a reasonable distance, whether it has capacity for your demand, the indicative connection point and route, and the indicative commercial terms or at least the connection charge basis. A reply saying that connection is not currently possible is a perfectly good outcome, provided it is in writing and reasoned.

Designing for future connection

Where connection is not possible now but a network is planned or a priority area applies, the scheme has to be built so it can connect later. Safeguarding costs little at design stage and is close to impossible afterwards.

Show these items on the drawings rather than describing them in text:

• A plant room or energy centre of sufficient size to house a future heat exchanger and associated plant, with access for replacement.
• A pipe route from the site boundary to the plant room, through accessible builder's work rather than through structure.
• A capped connection point at the boundary at an agreed position and depth.
• Space for valve sets, metering and pressurisation.
• A distribution system designed for low flow and return temperatures, so that a future network connection does not require re-piping the building.

The flow temperature point is the one most often overlooked. A communal system designed around 80 degrees flow cannot be connected to a low temperature network without replacing emitters, which means the safeguarding was nominal.

Communal systems where no network exists

A communal system has its own penalties, and the Energy Statement should quantify them rather than treating communal provision as automatically better.

Distribution heat losses from pipework running through risers and corridors are real, they continue all year, and they appear in the primary energy result. Model them rather than applying a default. The same pipework contributes to corridor temperatures, which feeds into the overheating assessment for the dwellings adjoining those corridors.

Where the heat source is a heat pump serving a communal loop, the flow temperature, the buffer strategy and the domestic hot water approach drive the system efficiency more than the headline coefficient of performance does. State the seasonal performance assumed and where it comes from.

Where combustion plant is proposed, including any gas backup, the flue has to be designed and assessed, and the dispersion modelling behind an energy centre flue height is usually required alongside the energy statement rather than after it.

Carbon factors applied to heat sources

The carbon and primary energy results depend entirely on the factors used, and three rules keep this defensible.

Use the factors from the current national calculation methodology for grid electricity and for gas, and state the version. Where a heat network connection is proposed, use the network's actual carbon intensity supported by evidence from the operator, not a generic district heating factor. And where the network's intensity is expected to improve, present the current figure as the compliance case and the improved figure as additional information rather than the other way round.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it, and verify the current London Plan policy text, which is under review.

Conditions securing the connection

Expect one of three mechanisms, and read the drafting before accepting it.

A condition requiring the safeguarding measures to be provided and retained is the most common and the least contentious. A condition requiring connection if a network becomes available within a defined period places a future obligation on the occupier or the management company, and the period and the trigger need to be precise enough to be enforceable. An obligation in a section 106 agreement is used where a financial contribution towards network infrastructure is involved.

An illustrative example

A 220 unit scheme in a heat network priority area submits an enquiry log showing three letters over four months to the borough energy team and to a nearby network operator. The operator confirms a network exists 600 metres away with capacity, but with no planned extension to the site within the development programme. The scheme provides a communal ambient loop with heat pumps, a safeguarded plant room, a capped connection at the boundary, and a 45 degree flow temperature distribution system. This example is illustrative rather than a real assessment.

The Sustainability Statement should quote the same figures as the energy chapter, because inconsistency between the two is the quickest way to lose an officer's confidence in both.

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