Be Lean, Be Clean, Be Green, Be Seen: the energy hierarchy

Be Lean, Be Clean, Be Green, Be Seen is the London Plan energy hierarchy, and every energy statement for a major application in London has to be structured around those four steps in that order. The first three are design stages: reduce demand, supply what remains efficiently, then generate the rest from renewable sources. The fourth is a reporting duty that follows the building into use, and it is the one that catches teams out because it does not end when the scheme is built.

Where the four step hierarchy comes from

The hierarchy sits in the London Plan's policy on minimising greenhouse gas emissions, which requires major development to be net zero-carbon and sets a minimum on-site reduction against the Building Regulations baseline. The Greater London Authority publishes guidance on how energy assessments should be prepared and reported.

Two numbers drive the structure. Major development is expected to achieve a minimum on-site carbon reduction beyond the Part L baseline, and within that, a portion has to come from energy efficiency alone at the Be Lean stage before any supply-side or renewable measures are counted. Residential and non-residential schemes have different efficiency-only figures.

Presenting the stages out of order, or claiming the Be Lean figure with contributions from a heat pump, is the most common reason a borough's energy adviser sends an assessment back. Report each stage separately, with the regulated emissions after each step in the same table.

Be Lean: fabric and demand reduction

This stage is about the building rather than the plant. Improved U-values, better airtightness, reduced thermal bridging with calculated psi values rather than default figures, glazing ratios tuned by orientation, efficient ventilation with heat recovery, and lighting and controls.

Passive measures earn their place here because they last. A fabric decision made now still performs in forty years, while a heat pump will be replaced two or three times over the same period. And the assessor's model rewards them consistently, which is not true of every renewable technology.

Calculated thermal bridging is worth the effort. Default psi values in the compliance software are deliberately conservative, and a set of calculated junction details on a well-detailed scheme can move the Be Lean figure by enough to avoid an offset payment. It is one of the few improvements that costs drawing office time rather than capital.

The tension is with overheating. Reducing heat loss and increasing airtightness raises overheating risk, and the same scheme has to pass a dynamic thermal model. Where the Overheating Risk Assessment and the energy strategy are done sequentially by different consultants, they usually conflict. Run them together and let the glazing and shading decisions serve both.

Be Clean: heat networks and efficient supply

The second stage asks how the remaining demand is supplied. London policy sets an order: connect to an existing or planned district heat network where one is available, then consider a site-wide network, then communal systems, before falling back to individual systems.

Two things have changed the practical answer. Gas combined heat and power has fallen out of favour as the grid has decarbonised, and air quality policy in London makes combustion plant harder to justify. Heat network connection now usually means a low-temperature or ambient-loop network with heat pumps rather than a gas-fired one.

Where a network connection is proposed but not yet available, the assessment has to show connection readiness: plant space, a route, and a commitment to connect when the network reaches the site. That commitment is normally secured by condition or in a section 106 agreement, so raise it early rather than at the drafting stage.

Communal systems carry their own risk. Distribution losses from poorly insulated risers push corridor temperatures up and undermine the overheating case, so specify pipework insulation standards and low flow temperatures in the same document.

Be Green: renewables and the residual shortfall

The third stage covers on-site renewable generation, in practice photovoltaic panels and heat pumps, and it is where the remaining regulated emissions are addressed.

Heat pumps do most of the work in this stage now, and the modelling assumptions behind them matter. A seasonal coefficient of performance taken from a manufacturer's headline figure, rather than from the flow temperatures the system will actually run at, inflates the result and will be picked up when in-use data is reported.

Roof space is the constraint. Photovoltaic arrays compete with plant, terraces, green roofs, lift overruns and any biodiverse roof required by the biodiversity or urban greening policies. Resolve that competition on a roof plan at the design stage and show it in the submission, because an energy statement claiming an array area that the roof plan cannot accommodate is easily checked.

Where the on-site target still cannot be met, the shortfall is dealt with through a cash in lieu contribution to the borough's carbon offset fund. The payment is calculated on the residual tonnes of carbon over a defined period at a price per tonne recommended by the Mayor and adopted by the borough. Both the price and the period should be taken from the current guidance rather than from an earlier scheme.

Be Seen: post-construction monitoring

The fourth stage is the one that changes behaviour. Development subject to the policy has to report actual energy performance data through the Greater London Authority's monitoring platform at defined stages: as designed at planning, as built at completion, and then in use for a period of years after occupation.

That means the assumptions in your planning stage assessment are eventually compared against metered reality. A scheme that claimed an ambitious heat pump coefficient of performance, or a photovoltaic yield calculated without shading, will show the gap.

Reporting duties are usually secured by condition or by an obligation in the legal agreement, and they bind whoever owns and operates the building. Flag that to the client at the outset, because it affects metering strategy, the building management system specification and the operational handover, none of which is inexpensive to add later.

• Metering has to be granular enough to separate landlord and tenant energy and to identify each end use.
• Someone has to own the reporting duty for the whole monitoring period, which on a build to sell scheme means the management company.
• Data has to be submitted in the specified format at the specified stages.

How this affects the documents you submit

An energy assessment structured to the hierarchy is a specific document with a specific shape. The Energy Statement should carry a stage-by-stage emissions table, the modelling assumptions, the heat network position, the roof plan showing the array, and the offset calculation if there is a shortfall.

It sits alongside rather than inside the Sustainability Statement, which covers the wider policy set, and alongside the Whole Life Carbon Assessment for referable schemes. All three should describe the same building. Reviewers cross-check floor areas, unit numbers and services strategies between them, and inconsistency is the fastest way to a request for further information.

Outside London the four stage language is not policy, though many authorities apply a similar hierarchy through their own climate policies. Use the structure by all means, and cite the local policy that applies rather than a London policy that does not.

This is general guidance, not legal advice, and London Plan targets, offset prices and monitoring requirements are updated periodically, so check the current guidance before relying on any figure. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.