The energy hierarchy sections of an Energy Statement

An Energy Statement is not a single calculation with a single answer. It is four calculations reported in sequence, each showing what the previous stage left to do. Be lean, be clean, be green, be seen: reduce demand, supply the remaining demand efficiently, generate what you can renewably, then report what the building actually does once people are in it.

Getting the energy statement be lean be clean be green structure right matters more than the final percentage, because a reviewer checks the stages before the total. A scheme that claims a large reduction with almost all of it arriving at the renewables stage tells them the fabric was never taken seriously.

What each stage has to demonstrate

The hierarchy is a sequence of constrained choices, not a menu. Each stage is assessed on what it delivers before the next one is applied.

Demand reduction comes first because it is permanent. Fabric performance stays with the building for its life, whereas a heat source is replaced every fifteen to twenty years and a tariff changes every year.

Efficient supply comes second: how the remaining demand is met, at what conversion efficiency, and whether a network connection is available.

Renewable generation comes third, sized against the demand that survives the first two stages rather than against the original figure.

Reporting comes fourth, and is the newest of the four. It covers what the building's measured energy use turns out to be after occupation, compared against what the statement predicted.

Each stage needs its own emissions figure and its own percentage saving against the baseline, plus a cumulative figure. Present them in one table early in the document, then explain them section by section.

Demand reduction and the measures that count

This section should read like a specification, not an aspiration. Numbers, not adjectives.

• Element by element U-values for walls, roof, floor, windows and doors, against the notional building values.
• Air permeability target, with the testing regime that will confirm it.
• Thermal bridging approach: accredited construction details, calculated psi values, or a default that penalises the result.
• Glazing ratio by orientation, with the daylight and overheating consequences acknowledged.
• Ventilation strategy and, where mechanical, the specific fan power and heat recovery efficiency.
• Lighting efficacy and controls in non-domestic space.

Two things reviewers look for. Whether the fabric specification in the energy model matches the one in the drawings and the design and access statement, because a mismatch surfaces at discharge of conditions. And whether the demand reduction stage does any real work, because a stage that delivers a token saving before a large renewables figure is the signature of a scheme designed around a photovoltaic array.

State the modelling tool and version, and append the output sheets. A summary table alone invites a request for the underlying files.

Efficient supply and where heat networks sit

The second stage asks how the remaining demand is met before renewables are considered.

Where an existing heat network runs near the site, connection is normally the expected answer and the statement has to address it explicitly, with evidence of an enquiry to the operator and the response. Where a network is planned but not built, the usual outcome is a connection-ready design: plant space, a hydraulic interface location, and pipe routes safeguarded, secured by condition or obligation.

Site-wide networks within a development are assessed on their own merits, and the calculation has to include distribution losses honestly, since a network serving a small number of very efficient dwellings can perform worse than individual plant.

Combined heat and power has moved a long way in a decade. Where the electricity grid has decarbonised, generating electricity on site from gas no longer produces the carbon saving it once did, and a statement proposing it needs to justify the choice with current emissions factors rather than with a template from an older scheme. Say which factors you used and for which year.

Heat pumps sit awkwardly across the second and third stages, and conventions differ between authorities. Pick one treatment, state it plainly, and apply it consistently.

Renewable generation and the roof

The third stage is where roof area becomes the binding constraint, and where energy statements most often part company with the architecture.

A roof plan belongs in this section showing the photovoltaic array set out against everything else competing for the same surface: plant, lift overruns, terraces, green roof, rooflights, maintenance access and safety zones. An array drawn edge to edge over a roof that also carries an air source heat pump farm is not a buildable proposal, and reviewers who have seen a hundred of these will spot it.

Overshadowing matters too. Panels on a lower roof shaded by the taller part of the same building generate far less than the headline capacity suggests, and the calculation should reflect the actual layout.

Report the array in both kilowatts peak and square metres, give the assumed orientation and pitch, and state the annual generation and the resulting emissions saving. Where the array cannot reach the policy target, say so at this point rather than burying it in the offset section.

Residual emissions and offset arrangements

When the three on-site stages are complete, whatever remains is residual, and policy in London and in a growing number of authorities requires it to be dealt with through a cash-in-lieu payment into the authority's carbon offset fund.

The calculation is mechanical: residual annual regulated emissions, multiplied by the policy period, multiplied by the price per tonne set by the authority. State each input separately so the officer can check it, and confirm the price you have used and its source, because the figure is periodically revised.

Two failure modes recur. Using an out-of-date price, which produces a payment the section 106 draft then has to correct. And treating the offset as the first resort rather than the last, which invites the officer to ask why the on-site stages stopped where they did.

Where the scheme also needs an Overheating Risk Assessment, run it against the same fabric and glazing assumptions. A tighter envelope with more glass improves the energy figure and can fail the thermal comfort criteria, and the reporting of those results is covered in reporting CIBSE TM59 results.

Monitoring and the reporting stage

The fourth stage commits the developer to reporting real performance rather than modelled performance, and it is the one most often treated as boilerplate.

In practice it means three submissions: the predicted figures at planning stage, the as-built figures once construction is complete, and in-use metered energy data over a defined period after occupation, typically several years. Metering has to be designed to produce that data, split between landlord and tenant supplies and between regulated and unregulated loads, which is a design decision made long before anyone thinks about reporting.

Name in the statement who will collect the data, how it will be submitted and over what period. A commitment without a named party is unenforceable in practice, even when it sits in an obligation.

Where embodied emissions are also assessed, the Whole Life Carbon Assessment should share the same area schedule and specification as the Energy Statement. Reviewers compare them, and a gross internal area that differs between the two is the quickest way to trigger a round of clarification.

Browse the PlanScope report types to see which energy and carbon documents a scheme is likely to need.

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