Energy masterplanning across a phased site

An energy strategy written for an outline application will be obsolete before the last phase of a masterplan is built, and pretending otherwise produces conditions nobody can discharge. The fix is an energy masterplan for phased development that fixes the things which must be fixed at outline stage, the spatial and infrastructure decisions, and leaves the technology choice open to be settled phase by phase against the standards in force at the time.

Get that division wrong and you end up either with a condition requiring a technology that has been superseded, or with no commitment at all and a reserved matters negotiation that starts from nothing.

What an outline application can realistically fix

Outline permission establishes the principle and whatever matters are not reserved. On a large residential or mixed use scheme the energy strategy at that stage should fix four things.

The performance commitment, expressed as a percentage improvement against the relevant Building Regulations target or as an absolute carbon figure per phase. The spatial requirements: plant space, energy centre location and footprint, service corridors and easements. The connection obligations, including whether each phase must be designed to allow connection to a district heat network. And the governance: who reports what, when, and to whom.

What it should not fix is the equipment. A condition naming a specific heat pump refrigerant, boiler type or photovoltaic capacity will either be varied later or quietly ignored.

Phasing the strategy against the build out

Set the strategy out phase by phase, with a table in the Energy Statement showing for each phase the expected start, the regulatory baseline that will apply, the carbon target, and the measures assumed.

The regulatory baseline is the moving part. Part L was uplifted in 2021, and the Future Homes Standard has been announced as a further step, so a phase starting several years after outline permission will be built to a different target from phase one. Where a commitment is expressed as an improvement on the regulations in force at the time of the reserved matters submission, it keeps its meaning as the baseline tightens. Where it is expressed as an improvement on a named 2021 baseline, it gradually becomes meaningless.

State the hierarchy you are applying. On London schemes the be lean, be clean, be green, be seen sequence in the London Plan is the expected structure, and the Greater London Authority publishes guidance on how each stage is reported.

Safeguarding routes, plant space and easements

This is the part that cannot be retrofitted, and it is where an outline application earns its money.

Reserve the energy centre plot on the parameter plans, with a footprint and height that a plant room at the final phase could actually use. Undersizing it is common, because the early phases need less plant than the completed scheme.

Route the primary pipework corridors on the infrastructure plan, avoiding adoptable highway where possible, and secure easements through the section 106 or through the plot sale documentation. A heat main that has to cross land sold to a housebuilder in phase two, with no easement, will not be built.

Allow riser space and plant space within the plots themselves, and set the requirement in a design code rather than leaving it to individual plot designers. Heat pumps need more space than boilers, both for the units and for the hot water cylinders, and a plot layout drawn around a combination boiler cupboard will not take them.

Reserved matters conditions that stay deliverable

Write conditions that ask for a process and an outcome, not a product.

A condition requiring submission of a phase specific energy statement before commencement of that phase, demonstrating the agreed percentage improvement against the regulations then in force, with as built evidence submitted before occupation, is deliverable in any technology scenario. A condition requiring the installation of the specific system described in the outline energy statement is not.

Watch the trigger points. Pre-commencement conditions on a phased scheme should be drafted to bite phase by phase rather than across the whole site, otherwise phase one cannot start until information about phase six has been approved. The practical drafting points are covered in carbon reduction planning conditions and how to discharge them.

Include a review mechanism. Where a phase cannot meet the agreed target using the technology then available, an agreed process for demonstrating why, and for making up the shortfall elsewhere or through a carbon offset payment, avoids a stalemate.

When the technology changes between phases

It will. Schemes consented a decade ago with gas fired combined heat and power now look very different, and schemes consented today on air source heat pumps may look different again by the time their later phases are built.

Design for succession rather than for a single answer. That means a heat network designed to operate at a temperature a future heat source can supply, plant space sized for the bulkier option, electrical capacity secured from the distribution network operator for the full scheme rather than phase by phase, and a fabric standard that does not depend on the heat source at all.

Fabric is the part that ages best. Insulation, airtightness and glazing specification set at outline stage are still delivering in phase eight, whereas the plant will have been replaced at least once.

Where a statutory heat network zone covers the site, connection may become a requirement rather than an option under the zoning framework introduced by the Energy Act 2023, and the commencement of those provisions is worth checking before assuming a standalone solution is safe. The implications are set out in the note on heat network zoning and the connection requirement.

Carbon accounting across a long programme

Operational carbon is reported per phase against the baseline then applicable, which is straightforward once the commitment is drafted properly.

Embodied carbon is harder. A whole life carbon assessment prepared at outline stage relies on assumed quantities and generic data, and the figures will move once a contractor is appointed and real product data is available. Treat the outline assessment as a target setting exercise, and require an updated Whole Life Carbon Assessment at reserved matters for each phase using the methodology current at the time.

Be careful with grid decarbonisation assumptions. The carbon factor applied to electricity changes over time, and a strategy that relies on the grid improving to meet its target is making a claim about someone else's performance rather than its own.

Obligations that survive a land sale

Most large phased sites change hands, either wholesale or plot by plot, and the energy strategy has to survive that.

Planning obligations bind the land, so a section 106 obligation on energy performance runs with the title and binds successors. That is the durable mechanism. Conditions attach to the permission and bind whoever implements it, which is also effective, but conditions are easier to vary later.

Three things worth putting in the obligation on a scheme with a heat network: the easements, the obligation to connect each phase or to design for connection, and the customer protection arrangements for residents who will be buying heat from a monopoly supplier. That last one is increasingly asked for by authorities, and it is easier to agree at the outset than to impose later.

Draw the energy centre and the pipe corridors on the parameter plans, express the commitment against the regulations in force at each phase, and draft the conditions phase by phase. Everything else can be decided later. You can also check which reports a phased scheme is likely to need before the outline submission is fixed.

This is general guidance, not legal advice. Energy and carbon assessment is specialist work and professional review is strongly advised. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.