AES Sustainability Consultants
Based in Tiverton, Devon · Covers England, Scotland and Wales Accreditation stated by provider: ATTMA, SITMA, Elmhurst, ECMK, TrustMark, BREEAM, PassivhausOwn websiteUK-wide
02 · Building Regulations · Part L
SAP calculations
A SAP calculation shows building control that a new home, conversion or heavily glazed extension meets the energy and carbon targets in Part L of the Building Regulations. New homes usually need one twice: at design stage, and again as built before completion.
DWGuide by Dan Wallis · Updated 27 September 2026
This guide covers the rules in England. See Wales, Scotland and Northern Ireland.
Who needs oneAnyone building a new home, converting a building into homes, or adding a heavily glazed extension
Who can do itAn On-Construction Domestic Energy Assessor (OCDEA) registered with an accreditation scheme
WhenDesign stage before work starts; as-built stage at completion
93 SAP assessors listed across the UK
Featured (paid) listings first, then A–Z · How we check listings
Find SAP assessors by region
London (22) South East (12) East of England (12) South West (9) West Midlands (14) East Midlands (5) Yorkshire and the Humber (5) North West (15) Wales (3) Scotland (4) Northern Ireland (11)
National providers (55)
Air Testing UK Ltd
Based in Manchester · Covers Nationwide Accreditation stated by provider: iATS, BINDT, BPEC, AECBOwn websiteUK-wide
Airtight Testing Staffordshire
Based in Stoke-on-Trent · Covers Staffordshire and UK-wide Accreditation stated by provider: ATTMAOwn websiteUK-wide
Apex Home and Energy Surveyors
Based in Warrington, Cheshire · Covers Warrington and WA postcodes for EPCs; calculation work across England and Wales Accreditation stated by provider: RICS, Elmhurst Energy, CHASOwn websiteUK-wide
APT Sound Testing (Air Pressure Testing Ltd)
Based in Upper Sundon, Bedfordshire · Covers Coventry, Warwickshire and UK-wide Accreditation stated by provider: UKAS accredited testing laboratory (No. 4340)Own websiteUK-wide
Assessment Hive
Based in Goffs Oak, Hertfordshire · Covers London and throughout the UK Accreditation not yet checkedOwn websiteUK-wide
ATSPACE
Based in Royston, Hertfordshire · Covers England and Wales Accreditation stated by provider: Elmhurst, NHER, SITMA, TrustMark, Passivhaus Trust (Patron), BPEC, BSRIA, Passivhaus Trust PatronOwn websiteUK-wide
Base Energy
Based in Staines-upon-Thames, Surrey and Bootle, Merseyside · Covers UK-wide, including London Accreditation stated by provider: Elmhurst, CIBSE, TrustMark, BREEAMOwn websiteUK-wide
Briary Energy
Based in Hatfield, Hertfordshire · Covers UK-wide Accreditation not yet checkedOwn websiteUK-wide
Build Energy
Based in UK (several offices) · Covers UK-wide Accreditation not yet checkedOwn websiteUK-wide
Building Energy Experts
Based in Bristol · Covers Nationwide Accreditation stated by provider: Elmhurst, ATTMA, TrustMark, Retrofit Academy (Corporate Member), Retrofit Academy Corporate Member, AECBOwn websiteUK-wide
Complete EPC
Based in Finchley, London · Covers All of London, and elsewhere in the UK Accreditation stated by provider: Quidos, StromaOwn websiteUK-wide
Compliance 4 Buildings
Based in Hornchurch, Essex · Covers Nationwide (UK) Accreditation stated by provider: ATTMAOwn websiteUK-wide
Coventry Property Certification
Based in Coventry, West Midlands · Covers England and Wales Accreditation not yet checkedOwn websiteUK-wide
DAA Group
Based in London · Covers Nationwide across the UK Accreditation stated by provider: ATTMA, BPECOwn websiteUK-wide
Designed 2 Comply
Based in Chorley, Lancashire · Covers Whole of the UK Accreditation stated by provider: OCDEAOwn websiteUK-wide
E2 Specialist Consultants
Based in Birmingham office (head office Wakefield) · Covers Birmingham and 25+ West Midlands towns Accreditation stated by provider: SITMA, iATSOwn websiteUK-wide
Easy EPC Ltd
Based in Brighton, East Sussex · Covers Nationwide, with local landing pages for many UK towns including Leicester, Nuneaton and Coventry Accreditation not yet checkedOwn websiteUK-wide
Elmstead Energy Assessments & Building Services (EEABS)
Based in Colchester, Essex · Covers UK-wide, including London Plan energy assessments Accreditation stated by provider: Elmhurst, CIBSE Low Carbon Consultant, CIBSE Low Carbon Energy Assessor, EDSL TASOwn websiteUK-wide
Energist
Based in Cirencester, Gloucestershire · Covers Nationwide Accreditation stated by provider: Elmhurst, ATTMA, ANCOwn websiteUK-wide
Energy & Design
Based in Cannock, Staffordshire · Covers England, Scotland and Wales Accreditation stated by provider: Scotland Section 6 Approved Certifier of Design, BREEAM UK New Construction (Residential)Own websiteUK-wide
Energy Counsel
Based in Manchester, Greater Manchester · Covers Manchester, the North West and nationwide Accreditation stated by provider: CIBSE, BPEC, iATS, SITMA, BREEAM, AECB, ConstructionlineOwn websiteUK-wide
Energy National
Based in Rochdale, Greater Manchester · Covers Greater Manchester and East Lancashire locally; SAP work nationwide Accreditation stated by provider: Elmhurst Energy, Stroma, ABBE, BRE, TrustMarkOwn websiteUK-wide
Energycount
Based in Poole, Dorset · Covers Nationwide (UK) Accreditation not yet checkedOwn websiteUK-wide
Energytest
Based in Tunbridge Wells, Kent · Covers London and the South East; nationwide Accreditation stated by provider: ATTMAOwn websiteUK-wide
EnergyWise Services
Based in Belfast, Northern Ireland · Covers UK-wide (remote delivery available) Accreditation not yet checkedOwn websiteUK-wide
enevo
Based in Birstall, West Yorkshire · Covers UK-wide (national network of local assessors) Accreditation stated by provider: ATTMA, iATS, SITMA, Elmhurst, Stroma Certification, BREEAM, ABBEOwn websiteUK-wide
Environmental Economics
Based in Luton, Bedfordshire · Covers UK nationwide, including London Plan work Accreditation stated by provider: Elmhurst (overheating scheme)Own websiteUK-wide
EPC Assess Ltd
Based in Midlands · Covers Birmingham, Wolverhampton, Coventry and UK-wide Accreditation not yet checkedOwn websiteUK-wide
EPC Experts
Based in Coventry, West Midlands · Covers Coventry, Nuneaton, Rugby, Warwick and nationwide Accreditation not yet checkedOwn websiteUK-wide
EPC National
Based in Heywood, Greater Manchester · Covers Nationwide Accreditation not yet checkedOwn websiteUK-wide
ERS Consultants
Based in Oxford · Covers UK residential and commercial developments Accreditation not yet checkedOwn websiteUK-wide
Fading Footprints Ltd
Based in Leeds, West Yorkshire · Covers Nationwide (UK) Accreditation not yet checkedOwn websiteUK-wide
Focus 360 Energy
Based in UK (several offices) · Covers Nationwide Accreditation stated by provider: Elmhurst, ECMK, StromaOwn websiteUK-wide
Gradwell Group
Based in Doncaster, South Yorkshire · Covers England-wide Accreditation not yet checkedOwn websiteUK-wide
HA Acoustics
Based in Harlow, Essex · Covers East Anglia, London, South West and nationwide Accreditation stated by provider: UKAS, iATSOwn websiteUK-wide
Manchester EPC Ltd
Based in Cheadle, Greater Manchester · Covers EPC visits within about 50 miles of Manchester; SAP and new-build work nationwide Accreditation not yet checkedOwn websiteUK-wide
Melin Energy Consultants
Based in Swansea · Covers UK-wide (offices in Swansea, Bristol and London) Accreditation stated by provider: Elmhurst (Approved Psi Value Competency Scheme), BREEAM AP, CIBSE, UK Thermography AssociationOwn websiteUK-wide
MES Building Solutions
Based in Newark, Nottinghamshire · Covers Throughout the UK (offices in Newark, London and Birmingham) Accreditation stated by provider: ATTMA, Elmhurst, AECB, TrustMarkOwn websiteUK-wide
MSAFE
Based in Bournemouth, Dorset · Covers Nationwide Accreditation stated by provider: UKAS (sound insulation testing)Own websiteUK-wide
PB Sustainability
Based in Wirral, Merseyside · Covers Nationwide Accreditation stated by provider: ABBE, CABE, ElmhurstOwn websiteUK-wide
Purple Energy Solutions
Based in UK (several offices) · Covers Nationwide Accreditation stated by provider: ATTMA, UKASOwn websiteUK-wide
QuinnRoss Energy
Based in Sittingbourne, Kent · Covers UK-wide, with a focus on Greater London and the South East Accreditation stated by provider: Elmhurst, UKAS, BRE Global, CIBSE Low Carbon Consultant, Low Carbon Energy AssessorOwn websiteUK-wide
Ratio Seven
Based in Nantwich, Cheshire · Covers Nationwide including Birmingham and the West Midlands Accreditation not yet checkedOwn websiteUK-wide
sap2sbem
Based in Leek, Staffordshire · Covers UK-wide (desk-based) Accreditation stated by provider: ElmhurstOwn websiteUK-wide
SAPgen
Based in Warrington, Cheshire · Covers UK-wide Accreditation stated by provider: Elmhurst (OCDEA)Own websiteUK-wide
SAPs UK
Based in London · Covers UK-wide, including Scotland Accreditation stated by provider: Elmhurst (NHER)Own websiteUK-wide
SEES
Based in Durley, Southampton, Hampshire · Covers UK-wide Accreditation stated by provider: Elmhurst, ATTMA, BREEAM licensed assessor company, Stroma certifiedOwn websiteUK-wide
Shire Group BSC
Based in Birmingham · Covers Nationwide (UK) Accreditation stated by provider: CIBSE Low Carbon ConsultantOwn websiteUK-wide
Sound Solution Consultants
Based in Ipswich, Suffolk · Covers Nationwide Accreditation stated by provider: UKAS, IOAOwn websiteUK-wide
Southern Assessors
Based in Salisbury, Wiltshire · Covers UK-wide, with offices in London, Bristol and Birmingham Accreditation stated by provider: NHEROwn websiteUK-wide
Stroma Built Environment
Based in Wakefield, West Yorkshire · Covers UK-wide Accreditation stated by provider: UKAS (No. 2731), ATTMAOwn websiteUK-wide
UK Building Compliance
Based in Hinckley, Leicestershire · Covers UK-wide (England, Wales, Scotland and Northern Ireland) Accreditation stated by provider: ATTMA, Elmhurst, SITMA, BPEC, UKASOwn websiteUK-wide
Vision Energy & Sustainability
Based in Bollington, Cheshire · Covers UK-wide Accreditation not yet checkedOwn websiteUK-wide
Regional providers (check they cover your area) (1)
UKSAPS
Based in Royston, Hertfordshire · Coverage not stated, so check with the provider Accreditation not yet checkedOwn website
When do you need SAP calculations?
- New homes. Every new dwelling needs a design-stage SAP before work starts, and an as-built SAP with an on-construction EPC at completion.
- Conversions that create a new home, such as barns, offices or space above shops.
- Extensions over the glazing limit in Approved Document L, or where you want to trade off the performance of one element against another.
Design stage vs as-built
Before work starts
Design-stage SAP
Worked out from your drawings and specification. Building control uses it to check the design can meet Part L.
At completion
As-built SAP
Updated with what was actually built, including the air test result, and used to produce the on-construction EPC.
What your assessor will ask for
- Floor plans, elevations and sections with dimensions
- Wall, floor and roof build-ups, and window and door specifications
- Heating, hot water and ventilation systems, and any solar PV
- For the as-built stage: the air test result and photographic evidence of how key details were built
Future Homes Standard. From 24 March 2027, new homes in England are assessed against the Future Homes Standard using SAP 10.3. The Home Energy Model will replace SAP later, with a changeover period of at least two years.
In Wales, Scotland and Northern Ireland
This guide describes the rules in England. Building regulations are devolved, so here is how SAP calculations works in the rest of the UK.
Wales
Every new home needs design-stage and as-built SAP under Wales’s own Part L. Wales uses SAP 10.2 today, with a Welsh compliance report (BRWL) instead of England’s BREL. From 4 March 2027, new Welsh rules move to SAP 10.3 and require on-site renewables, usually solar PV, on new homes.
Scotland
New homes must meet Section 6 (Energy) of the Scottish Technical Handbook, using SAP 10.2 in software approved for Scotland. The design-stage SAP goes in with the building warrant application, and the as-built SAP with the completion certificate.
Northern Ireland
New homes are assessed under Technical Booklet F1 (2022), which still uses SAP 2009 rather than SAP 10. The design-stage calculation goes in with the building control application, and the as-built result goes to the council within 5 days of completion.
Common questions
How much do SAP calculations cost?
It depends on the size and complexity of the home and whether you need design-stage and as-built calculations together. Providers set their own prices, so compare quotes.
Do I need a SAP calculation for an extension?
Usually not, unless the extension goes over the glazing limit or your building control body asks for one to show compliance.
What's the difference between SAP and an EPC?
SAP is the calculation method. The on-construction EPC is the certificate produced from the as-built SAP when a new home is finished.
Can any energy assessor do new-build SAP?
No. New-build SAP needs an On-Construction Domestic Energy Assessor (OCDEA) registered with an accreditation scheme. Assessors who only do EPCs on existing homes are not qualified for it.
Is SAP being replaced?
Eventually. The Home Energy Model will replace it, but SAP 10.3 is the method when the Future Homes Standard starts in March 2027.
New to the jargon? See our glossary of terms, from air permeability to TrustMark.