What Part L 2021 changed for a planning energy statement

A part l 2021 energy statement reports three numbers for a dwelling, not one. The delivered emission rate against a target emission rate, the delivered primary energy rate against a target primary energy rate, and the fabric energy efficiency rate against its target. Statements that carry only the carbon figure are incomplete, and officers in authorities with an energy policy now ask for all three.

The bigger change is quieter. The carbon factor for grid electricity was revised downwards, which rearranged the answer to almost every question about heating a new home.

The three metrics an assessment reports

Under the 2021 uplift to Part L of the Building Regulations, a new dwelling has to satisfy targets on emissions, on primary energy and on fabric performance at the same time.

Primary energy is the addition that surprises people. It counts the energy used at the building including the losses in generating and delivering it, expressed in kilowatt hours per square metre per year. A scheme can pass on carbon and fail on primary energy, which happens with direct electric heating where the low carbon factor flatters the emissions result while the primary energy demand stays high.

Fabric energy efficiency applies to dwellings and measures the space heating and cooling demand of the building fabric alone, before any consideration of the heating system. It is the metric that stops a poorly insulated house being rescued by a heat pump on paper.

Why the electricity carbon factor changed the answer

SAP 10 revised the carbon intensity of grid electricity from 0.519 kilograms of carbon dioxide per kilowatt hour under SAP 2012 to 0.136. That single change did more to reshape planning energy statements than any policy.

The consequence is straightforward. A gas boiler that looked acceptable against a 2013 baseline now sits badly against an electrically heated notional building, and heat pumps produce large carbon reductions on paper almost automatically. Schemes that previously reached their percentage improvement through photovoltaics now often reach it through the heat source.

That creates a trap in older local plan policies. A policy adopted in 2016 requiring a 19 per cent improvement over the Part L then in force means something quite different when the baseline and the carbon factors have both moved. Where a policy is expressed against a superseded edition, say so in the statement and show the comparison on both bases rather than choosing the flattering one.

Fabric energy efficiency and the notional building

The percentage improvement in a planning energy statement is measured against a notional building of the same size and shape as the proposal, built to a specification set out in Approved Document L. The 2021 edition tightened that specification, so the same real building scores a smaller improvement than it did against the previous baseline.

Read the current notional specification before writing any percentage into a statement. It changes what counts as an improvement, and where the notional building already includes a technology, installing that technology in the proposal does not by itself generate a saving against it.

This is where the energy hierarchy earns its place. Be lean, be clean, be green, be seen is not a slogan; it is an order of operations that keeps fabric measures from being displaced by generation. An Energy Statement that reports the reduction achieved at each stage of the hierarchy separately is far easier for an officer to check than one that reports a single headline figure.

Calculating an improvement without double counting

Set out the calculation as a sequence and show the intermediate figures.

1. The notional building result for emissions, primary energy and fabric energy efficiency.
2. The as-designed result after fabric measures only, which gives the lean stage saving.
3. The result after the heating and cooling strategy, which gives the clean stage saving.
4. The result after renewables, which gives the green stage saving.
5. The residual, and how any shortfall against policy is addressed.

The commonest double count is claiming photovoltaic output twice, once inside the building model and again as an additional renewable contribution. The second commonest is applying a carbon offset payment to a shortfall that has already been closed by on-site measures.

London schemes have their own layer. The London Plan sets an energy hierarchy and an on-site reduction target for major development, and Greater London Authority guidance sets out how the baseline is defined following the 2021 uplift. Check the current guidance rather than a previous scheme's assessment, because the methodology has been revised since the uplift took effect.

Errors that appear in the emissions table

Four recur often enough to be worth checking first in any statement you are reviewing.

Mixed carbon factors, where the baseline is calculated on SAP 2012 factors and the proposal on SAP 10. The numbers look excellent and mean nothing.

An improvement quoted against Part L 2013 with no statement of which edition was used, which makes the figure unverifiable.

Fabric figures reported for a sample dwelling and applied to a mixed block, where the worst-case flat is the one that fails.

Renewable output modelled with no shading analysis on a site with tall neighbours. Energy modelling assumptions officers challenge covers the wider set of inputs that attract scrutiny.

Evidence a case officer asks for

At planning stage the officer is not checking Building Regulations compliance, because that happens later and with a different body. What they want is enough to see that the policy target is achievable with the design submitted.

That usually means the software outputs for the notional and as-designed cases, a schedule of the fabric specification with U-values and air permeability, the heating and hot water strategy with the assumed system efficiency, the renewable capacity with its assumed area and orientation, and the resulting figures for all three metrics.

Overheating sits alongside this and is frequently forgotten. Part O introduced a separate compliance route for overheating in new residential buildings, and where a scheme relies on high glazing ratios with mechanical ventilation, an Overheating Risk Assessment prepared on the dynamic modelling route answers the question before the officer raises it. A design optimised for heating demand alone can fail in July.

Securing performance by condition

Conditions on energy performance need to be capable of discharge. A condition requiring development in accordance with the approved energy statement is enforceable. A condition requiring a stated percentage improvement without saying how it is demonstrated, or against which baseline, is a discharge argument waiting to happen.

Ask for wording that names the metric, the edition of Part L and the evidence required at each stage. Where post-construction verification is required, the usual evidence is the as-built compliance report, and the condition should say that rather than leaving it open. Similar drafting points arise on the optional water efficiency standard, which is imposed through the same mechanism.

One thing to watch as at September 2026. The Future Homes Standard is intended to replace the 2021 uplift, and the transitional arrangements around any change will govern which edition applies to a scheme already consented. Check the current position on gov.uk before committing a client to a specification that may need revisiting between permission and start on site.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.

Browse all 66 PlanScope report types to see how an energy statement fits with the rest of a submission.