Technical review: How Scottish non-domestic EPC ratings may change from October 2026

1. Purpose of this note

“In 2023 the ratings changed because the carbon factors changed. What are the technical ways a non‑domestic rating will change under the new Energy Performance of Buildings (Scotland) Regulations 2025?”

This briefing explores the technical mechanism of change for non‑domestic EPC ratings in Scotland, focusing on how the rating is calculated and banded, and why outcomes may differ from the current system even where the building itself is unchanged.

Reference (Scottish Government – non‑domestic research): https://www.gov.scot/publications/energy-performance-buildings-scotland-regulations-2025-non-domestic-buildings-research

2. 2023 change vs 2026 reform – what is different technically?

The 2023 rating movement is best understood as a “parameter change”: the same underlying calculation engine was used, but updated carbon/emissions factors changed the kgCO₂/kWh applied to fuels (particularly electricity), which flowed through to the EPC outcome.

The 2026 reform is different. Scottish Government documentation describes a change in the non‑domestic rating system itself (how the Asset Rating is derived and how it is mapped into bands), including a shift from an absolute rating presentation to a revised / comparative approach. This is not limited to carbon factor updates.

Reference (Scottish Government – EPC reform government response): https://www.gov.scot/publications/energy-performance-buildings-scotland-regulations-2025-update-government-response-epc-reform-consultations/

3. Current technical basis for non‑domestic EPC ratings (pre‑reform)

Scottish Government guidance on the non‑domestic research notes that, under the current Scottish rating system (implemented in iSBEM v6.1.e and other government‑approved software), the Asset Rating (AR) is equal to the calculated Building Emissions Rate (BER) in kgCO₂/m², rounded to the nearest whole number. That AR is then mapped to an A–G band using the existing band thresholds.

Reference (Scottish Government – “EPC Rating and Scales” section): https://www.gov.scot/publications/energy-performance-buildings-scotland-regulations-2025-non-domestic-buildings-research/pages/2/

4. What changes technically under the 2025 Regulations (commencing 31 October 2026)

The Scottish Government’s non‑domestic research describes the “difference between the current and revised EPC rating systems” as lying in (i) how the AR is derived from the BER and (ii) how that AR is mapped onto a revised band scale. The research refers to running test cases under the current software baseline (v6.1.e) and a revised implementation (v6.2.a) for comparison.
In practice, this means that even if your modelled BER stays similar, the rating outcome can change because the conversion from BER → AR and the A–G band thresholds are being revised.

Reference (Scottish Government PDF – non‑domestic research): https://www.gov.scot/binaries/content/documents/govscot/publications/research-and-analysis/2025/10/energy-performance-buildings-scotland-regulations-2025-non-domestic-buildings-research/documents/epc-reform-2025-non-domestic-buildings-research/epc-reform-2025-non-domestic-buildings-research/govscot%3Adocument/epc-reform-2025-non-domestic-buildings-research.pdf

5. Illustrative example: Office, retail and industrial building – old vs new (Energy Performance Rating focus)

Important: The Scottish Government research provides illustrative modelling and discusses revised rating scales; however, it does not provide a single, universal “band conversion table” that allows an EPC band from the old system to be deterministically converted into a new band without re‑running the calculation in the reformed methodology. The illustrative examples below show the mechanism of change using a simple, transparent worked example (hypothetical numbers) to demonstrate why a building may move band under the revised approach. You should treat these as illustrative only and not as predicted outcomes for any specific property.

Building type (illustrative) Old method (v6.1.e): BER→AR and old band New method (v6.2.a): BER→EPR/AR and revised band Why it can change (technical reason)
Office (typical heated/conditioned) Example: BER 18.4 → AR 18 (rounded) → Band D (old thresholds) Same BER 18.4 processed through revised mapping / revised thresholds → Band C (new thresholds) Revised mapping and band cut‑points can reclassify mid‑range buildings; comparative scaling can move distribution
Retail (high lighting / glazing sensitivity) Example: BER 28.6 → AR 29 → Band E Same BER 28.6 → revised mapping/thresholds → Band E or D (depending on new cut‑points) Retail archetypes can shift because the revised scale may treat high regulated electricity loads differently in banding
Industrial / warehouse (large volume, lower HVAC intensity) Example: BER 12.2 → AR 12 → Band C Same BER 12.2 → revised mapping/thresholds → Band B or C Re‑banding can improve apparent performance where older thresholds compressed low‑BER buildings into fewer bands

Reference (Scottish Government – modelling/test cases described, including current v6.1.e and revised v6.2.a comparisons): https://www.gov.scot/publications/energy-performance-buildings-scotland-regulations-2025-non-domestic-buildings-research/pages/4/

6. Legal and software context (NCM / approved tools)

Non‑domestic EPCs in Scotland are produced using government‑approved calculation tools under the National Calculation Methodology (NCM) framework (typically SBEM / iSBEM or DSM where appropriate). Under the reform, it is the approved methodology and its banding logic that changes, which is why results can differ even before you consider future updates to fuel carbon factors.

Reference (legislation.gov.uk – draft instrument contents, Energy Performance of Buildings (Scotland) Regulations 2025): https://www.legislation.gov.uk/sdsi/2025/9780111063866/contents

7. Practical implications for owners, landlords and transactions

Because the technical basis changes (not just carbon factors), two key implications follow: (1) portfolio ratings may “re‑base” when re‑assessed under the new regime; (2) it becomes risky to infer future bands from old EPCs. For owners planning transactions around and after the transition, the safest approach is to budget for fresh assessments and to treat the reformed rating as a new baseline for decision‑making.

Reference (Scottish Government – overview and commencement intent): https://www.gov.scot/publications/energy-performance-buildings-scotland-regulations-2025-update-government-response-epc-reform-consultations/

8. Disclaimer

This exploratory article is provided for general information purposes only and is intended to summarise the current position based on publicly available Scottish Government and Parliamentary/legislation information. It does not constitute absolute technical or legal advice and should not be relied upon as such. The application of the Regulations may vary depending on individual circumstances, and the legislative position and associated guidance may change. Readers should seek independent legal advice from their solicitor before taking action or making decisions based on the content of this document.