Regulated and unregulated energy: why the split matters

Regulated energy is the part of a building's energy use that Part L of the Building Regulations controls: space heating and cooling, hot water, ventilation, fixed internal lighting and the pumps and fans that serve them. Unregulated energy is everything else the occupier plugs in or switches on, from ovens and washing machines to lifts, external lighting, servers and catering equipment. Almost every planning policy target on carbon bites on the regulated half only, which is why a scheme can hit a 35 per cent improvement on paper and still use more energy than the building next door.

For an architect writing an energy statement, the split decides what you model, what you report and what claim you can honestly make.

Where the line falls

The regulated list follows the compliance calculation. For dwellings that is the Standard Assessment Procedure, for other buildings the National Calculation Methodology, and both assess a defined set of end uses under standardised occupancy assumptions. Anything outside that set is invisible to the compliance result.

Lifts are the item that surprises people. A tall residential block can spend a meaningful share of its landlord energy on lift motors and the associated standby loads, and none of it appears in the regulated figure.

Why policy targets stop at the regulated boundary

Because that is where the evidence is. A planning authority setting a carbon target needs a number that can be calculated before construction, checked at building control, and enforced by condition. The regulated figure comes out of a compliance model that has to be produced anyway, which makes it inexpensive to require and hard to argue about.

Unregulated energy depends on who moves in, what they buy and how they live. Two identical flats can differ by a factor of two on appliance use alone. An authority that set a condition on unregulated consumption would be conditioning occupant behaviour, which it cannot enforce and should not try to.

The consequence is a gap between the language of policy and the reality of the building. A development described as achieving a large percentage reduction has achieved it against a notional building on regulated uses, under standard occupancy. That is a meaningful engineering comparison. It is not a prediction of the bill.

Where local policy has gone further

The London Plan is the clearest case of a policy framework reaching past the regulated boundary. Major development in London is expected to be net zero-carbon, with a minimum on-site reduction beyond Part L, and any shortfall met through a cash in lieu contribution to a borough carbon offset fund. Alongside that, the Greater London Authority's monitoring requirements expect schemes to report metered energy use in operation, which necessarily includes unregulated consumption.

That is a reporting duty rather than a target, and the distinction matters. Nobody is refused permission because a resident bought a tumble dryer. But a scheme that has to publish its actual energy use two years after occupation is a scheme where the design team has a reason to think about small power, lifts and landlord services at stage 3 rather than never.

Outside London, a growing number of adopted local plans set a space heating demand limit and an energy use intensity target, both expressed in kilowatt hours per square metre per year. Energy use intensity covers all end uses, regulated and unregulated, so those policies do cross the line. Check the adopted plan rather than assuming the regulated convention applies, and say in the Energy Statement which basis each figure is on.

Modelling the unregulated half

If you are reporting unregulated energy, the compliance tools are the wrong instrument. They apply standardised assumptions that exist to make buildings comparable, not to predict consumption. For a realistic estimate, use an operational energy method such as the CIBSE approach to evaluating operational energy, which models the actual equipment schedule, occupancy profile and small power density rather than the notional ones.

Three assumptions drive the answer, so state them explicitly:

• small power density in watts per square metre, and where it came from
• the occupancy profile, including hours and diversity
• the treatment of landlord services, lifts, car park ventilation and external lighting

An energy use intensity figure without those assumptions stated is not checkable, and an officer or reviewer will treat it as unverified. Where a scheme is phased or has a district system, the boundary questions multiply, and our note on energy masterplanning for a phased site covers how to keep them consistent across plots.

The performance gap, and how to write about it honestly

Measured consumption in completed buildings regularly exceeds the modelled figure. The reasons are well rehearsed: standardised assumptions that do not match real occupancy, construction quality that falls short of the design detail, controls that are commissioned poorly or overridden, and equipment the model never included.

The honest position in a planning document is to report both figures and label them. State the regulated improvement against Part L for the policy test. Then state the estimated operational energy use intensity, with the method and assumptions named, as the figure that describes how the building will actually perform. Where the two tell different stories, say so.

That approach also protects the applicant. A statement that reports only the regulated percentage, and is then quoted in marketing as though it described total energy use, is the kind of claim that comes back at you.

What this means for a net zero claim

Be precise about scope or do not make the claim. Net zero regulated carbon, with a defined offset payment, is a specific and defensible statement. Net zero operational carbon covering all energy uses is a much stronger claim and needs the unregulated loads estimated, the renewable generation calculated against them, and the residual dealt with. Net zero whole life carbon brings embodied emissions in as well, which is the territory of a Whole Life Carbon Assessment rather than an energy statement.

Illustrative example: a 60 flat scheme reports a 38 per cent reduction in regulated emissions against Part L through fabric measures, an air source heat pump and roof photovoltaics, with a carbon offset payment covering the residual. The same scheme estimates an operational energy use intensity that sits above the target in the emerging local plan, driven by small power and lift energy. Both figures appear in the statement, each labelled with its basis. Illustrative only.

Presenting it that way rarely costs an applicant anything at committee. Officers are used to the distinction, and a document that draws it clearly is easier to recommend than one that blurs it.

One point to verify at the time of writing: the Future Homes Standard has been consulted on and its final technical detail and the date it takes effect should be checked on gov.uk before a statement relies on them, because the notional building and the compliance metrics change with it.

This is general guidance rather than legal advice. Check the position with your local planning authority or a qualified professional before relying on it.

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