Energy statements: SAP assessor or energy consultant
A SAP assessor produces the Building Regulations compliance calculation. An energy consultant writes the planning document that answers the local plan's carbon policy. Knowing which you need avoids a revision at validation.
Whether you need a sap assessor or energy consultant depends on which document the council has asked for. An accredited assessor produces the calculation that demonstrates Building Regulations compliance. A consultant writes the planning document that explains how the scheme meets the local plan's carbon policy. On a single self-build they are often the same person wearing two hats, and on anything larger they are not.
Appointing only the assessor and hoping the software output will satisfy a validation requirement is the mistake that sends the most energy statements back for revision.
What each of them actually produces
The accredited assessor produces a compliance calculation. For new dwellings that is a SAP calculation, run in approved software by an On Construction Domestic Energy Assessor, giving the target and dwelling emission rates, the primary energy figures and the fabric energy efficiency result. For non-domestic buildings it is an SBEM calculation by a non-domestic energy assessor, producing the BRUKL output that Building Control wants to see.
The assessor also lodges the Energy Performance Certificate at completion, which nobody else can do.
The consultant produces a narrative document. An Energy Statement for planning sets out the site constraints, works through the energy hierarchy, tests options that were rejected and says why, reviews heat network availability, calculates any residual emissions for offsetting, and demonstrates compliance with the specific policy the local plan contains. The SAP or SBEM outputs are evidence inside that document rather than the document itself.
Read the two side by side and the difference is obvious. One answers a regulatory test with a number. The other argues a planning case.
The accreditation behind a SAP calculation
SAP calculations for new dwellings must be produced by an assessor accredited through a scheme approved for the purpose, working in software approved for the current SAP methodology. The accreditation is personal, auditable and carries a member number that appears on the output.
That matters for three reasons. Councils occasionally ask for the assessor's accreditation number on validation. Building Control will not accept an unaccredited calculation. And the as-built calculation and the lodged certificate must come from an accredited assessor, so an unaccredited spreadsheet exercise at planning stage has to be redone later anyway.
There is no equivalent accreditation for writing an energy statement. Anyone can write one, which is why quality varies so widely, and why the more useful question to ask a prospective consultant is what they have had approved by the authority you are dealing with. Our note on what competent person means in planning legislation sets out where the law does impose a formal competence requirement, and energy statements are not on that list.
Where a local plan target needs more than SAP
SAP answers the Building Regulations question. Local plan policies routinely ask questions SAP was not built to answer.
| Policy requirement | What it needs beyond a SAP run |
|---|---|
| Percentage carbon reduction beyond the Building Regulations baseline | Two modelled cases, baseline and proposed, with the baseline edition stated |
| Reduction split between fabric and renewables | Staged modelling so each hierarchy step is reported separately |
| Net zero-carbon with offsetting | Residual emissions in tonnes, a 30 year period and the council's price per tonne |
| Heat network connection | Correspondence with the operator and a feasibility conclusion |
| Overheating avoidance | Dynamic thermal modelling, which SAP does not perform |
| In-use monitoring | A reporting protocol and a commitment secured by condition |
The overheating row is the one that trips self-builders. Compliance with Approved Document O can be shown by the simplified method in that document, but where a local policy requires assessment to CIBSE TM59 the work is dynamic thermal modelling in a different software environment, by someone with that specific skill. An Overheating Risk Assessment prepared for planning should say which route it followed, and our note on dynamic modelling competence for overheating assessments explains what to look for in the modeller.
Coordinating with the mechanical designer
The sequence that works is straightforward and frequently ignored.
- Fix the building form, orientation and glazing ratios with the architect, using a rough early SAP run to test them.
- Agree the heating and ventilation strategy with the mechanical designer before the energy statement is drafted, because the strategy is the statement's spine.
- Run the staged modelling once the strategy is fixed, so the hierarchy figures are real rather than reverse-engineered.
- Draft the planning document around those outputs.
- Re-run the calculation after any value engineering, before Building Regulations submission.
Step two is where self-builders lose money. A heat pump specified after the glazing schedule is fixed often needs a larger unit, more plant space and sometimes a buffer vessel that nobody allowed room for. Testing the fabric first reduces the plant, and reducing the plant reduces cost.
Ventilation is the other coordination point. An airtightness target below about 3 m³/h/m² at 50 Pa generally means mechanical ventilation with heat recovery rather than continuous extract, which changes the ducting strategy and the ceiling zones. That decision belongs to the mechanical designer, informed by the assessor's numbers.
As-built calculations, and who updates them
The design stage calculation is a prediction. The as-built calculation is the record, and it has to reflect what was installed.
The accredited assessor updates it, using the airtightness test result, commissioning data for the heating and ventilation systems, and any substitutions made during construction. The certificate is then lodged. Where the planning permission carries a post-construction reporting condition, somebody also has to prepare that submission, and the obligation usually sits with the consultant rather than the assessor because it references the approved energy strategy.
Two things go wrong here. Substitutions made on site are not reported back, so the as-built calculation fails and the airtightness test has to be repeated after remedial sealing. And the planning condition asks for evidence against the approved strategy, which nobody kept a copy of. Keep the approved energy statement, the approved drawings and the design stage calculation in one folder from the day permission is granted.
Deciding who to appoint, and when
For a single self-build outside a policy area with a carbon target, an accredited assessor is usually enough. Appoint them at the end of concept design, ask for an early indicative run before the glazing schedule is fixed, and budget for the as-built work and certificate.
Where the local plan sets a carbon reduction target, a net zero-carbon requirement, an overheating standard or a heat network policy, appoint a consultant as well, and appoint them before the layout is fixed. The scope letter should say who produces the modelling, who writes the planning document, who deals with discharge of conditions, and who prepares the as-built submission.
Ask three questions of anyone you are considering:
- Which accreditation do you hold, and which software do you use for the calculation?
- Have you had an energy statement approved by this authority, and what did the officer ask for that you had not included?
- Who updates the calculation if the specification changes during construction, and is that inside the fee?
A reviewer from the professional directory can check a draft energy statement before it goes in, which is often the quickest way to find the policy the document has not addressed. PlanScope drafts energy statements structured to UK planning policy and flags site-specific facts that are missing. Reports should be reviewed before submission, and we do not guarantee planning approval. For specialist technical reports, qualified professional input may be required.
This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.
Frequently asked questions
Can a SAP calculation on its own satisfy a validation requirement?
Rarely. A SAP calculation demonstrates Building Regulations compliance, while a validation list asking for an energy statement wants a narrative document working through the energy hierarchy against the local plan's carbon policy. The calculation belongs inside that document as evidence. Submitting the output alone is a common reason for a request for further information.
Does the person writing an energy statement need accreditation?
No formal accreditation exists for writing the planning document, unlike the personal accreditation an On Construction Domestic Energy Assessor holds for SAP work. That makes quality variable, so ask what the consultant has had approved by the authority you are dealing with and what the case officer asked them to add.
Who does the overheating assessment?
Compliance with Approved Document O can follow the simplified method in that document. Where local policy requires assessment to CIBSE TM59, the work is dynamic thermal modelling in different software and needs someone with that specific skill. State in the assessment which route was followed, because officers check.
When should the assessor be appointed?
At the end of concept design, with an indicative run before the glazing schedule and orientation are fixed. Fabric and form decisions are the ones that move the result, and an assessor brought in at technical design can only report what has already been designed. That usually means larger plant and higher cost.
Who updates the calculation if the specification changes?
The accredited assessor, using the airtightness test result, commissioning data and any substitutions. Where the permission carries a post-construction reporting condition, the submission usually falls to the consultant because it references the approved energy strategy. Settle both responsibilities in the appointment letter rather than during construction.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.