New EPCs from H2 2027 use four Home Energy Model metrics plus a legacy rating until 2029. What landlords must know about fabric, heating and smart readiness.
Home Energy Model dual metrics: what changes on EPCs from 2027 to 2029
Last updated: 25 July 2026
From the second half of 2027, domestic Energy Performance Certificates in England and Wales will be produced using the Home Energy Model (HEM) instead of SAP and RdSAP. That is not just a technical swap behind the scenes. Certificates will show four headline metrics , fabric performance, heating system, smart readiness and energy cost , alongside a legacy A–G rating that continues until at least the end of 2029.
For landlords, the shift matters because the Warm Homes Plan confirms private rented homes must reach EPC band C across two metrics by 1 October 2030. You will choose whether the second metric is smart readiness or heating system, alongside fabric performance.
This guide explains the SAP-to-HEM transition timeline, what each new metric measures, and how to plan upgrades before the switch.
Quick summary: SAP, HEM and the transition window
- Milestone: Today (2026) | What happens : RdSAP/SAP still produce all live EPCs; current MEES minimum is EPC E
- Milestone: Summer 2026 | What happens : Government to publish shared implementation plan with industry
- Milestone: H2 2027 | What happens : HEM-based EPCs launch; dual-running with SAP expected during transition
- Milestone: Until end 2029 | What happens : Legacy Energy Efficiency Rating (today's headline A–G) shown on new certificates
- Milestone: 1 Oct 2030 | What happens : PRS target: band C on two metrics (fabric + heating or smart readiness)
Source: HEM:EPC methodology paper (updated 17 March 2026); Warm Homes Plan.
Why SAP is being replaced
The Standard Assessment Procedure (SAP) and its reduced-data version RdSAP have underpinned domestic EPCs since the 1990s. They produce a single headline Energy Efficiency Rating (EER) from A to G.
Government and industry feedback has long flagged limitations: generic recommendations, weak representation of modern kit (heat pumps, batteries, solar, smart tariffs), and a single score that can hide poor fabric behind an efficient heating label , or vice versa.
HEM is a physics-based simulation engine. It models energy flows at finer granularity and separates the calculation core from policy-specific "wrappers". The HEM:EPC wrapper replaces RdSAP for existing homes and full SAP for new builds when reformed certificates go live.
The March 2026 methodology update pushed the domestic EPC launch from late 2026 to H2 2027, giving assessors and software providers time to retrain and beta-test. 2026 remains a preparation year , current EPCs still govern sales, lettings and grant eligibility.
The four new headline metrics
Reformed EPCs will display four banded metrics. Each answers a different question about the property.
1. Fabric performance
Measures thermal performance , insulation, glazing, airtightness , independent of the installed heating system. Government proposes using Fabric Energy Efficiency (FEE), adapted from Part L new-build methodology, with a standardised heating system substituted so fabric scores are not skewed by boiler type.
Landlord relevance: Fabric is expected to be one of the two metrics for MEES compliance. Loft insulation, cavity or solid wall insulation, floor insulation and high-performance glazing all feed this score. See our EPC C cost cap guide for how spend counts towards the £10,000 cap.
2. Heating system
Scores the efficiency and carbon intensity of the installed heating and hot water system. Proposals set the C/D boundary so direct electric resistance heating scores D or below, while heat pumps and storage-based technologies score higher.
Landlord relevance: You can elect heating system as your second compliance metric instead of smart readiness. BUS grants (£9,000 for oil-heated homes from July 2026) can help reach band C on this axis , but note BUS funding does not count towards the £10,000 MEES cost cap.
3. Smart readiness
Assesses potential to self-generate, store and shift electricity use , solar PV, batteries, smart controls, time-of-use tariffs and bidirectional EV charging. Properties where rooftop solar is impossible (some flats) may struggle to reach band C; exemptions are planned.
Landlord relevance: Choose this as your second metric if the property has strong solar/battery potential but fossil heating remains for now. Government explicitly offers landlord discretion between smart readiness and heating system for the secondary metric.
4. Energy cost
Shows estimated annual energy cost in pounds, not bands , a direct bill proxy using standardised fuel prices. Distinct from the legacy A–G rating.
Homeowner relevance: Useful for buyers and tenants comparing running costs. Less likely to be a MEES compliance metric but helps prioritise upgrades.
Legacy rating until 2029
New certificates will also show a Legacy Energy Efficiency Rating , the familiar A–G score , calculated via HEM but using the same methodology principles as today's EER. Government plans to display this until at least the end of 2029 so policies and grant schemes that reference the current rating can transition smoothly.
Important nuance: the legacy score will not match a current SAP-based EPC exactly, because HEM's consumption estimates differ. Treat it as comparable in band terms, not as a digit-for-digit match.
Existing EPCs commissioned before the switch remain valid for 10 years and count towards compliance until they expire, per the Warm Homes Plan.
Dual-metric MEES: what landlords must hit by 2030
The Warm Homes Plan states landlords must upgrade properties to EPC band C across two metrics by October 2030, unless a valid exemption applies.
Based on the HEM:EPC consultation and PRS consultation response:
- Compliance axis: Primary metric | Requirement : Fabric performance , band C
- Compliance axis: Secondary metric (landlord choice) | Requirement : Heating system band C or Smart readiness band C
- Compliance axis: Investment cap | Requirement : Up to £10,000 per property; cost-cap exemption if still below C
- Compliance axis: Spend backdate | Requirement : Improvements from 1 October 2025 count
- Compliance axis: Current rules until ~2027 | Requirement : EPC E minimum, £3,500 cap, £5,000 max fine
Worked example: choosing your second metric
- Property profile: Solid-wall terrace, old gas boiler, no roof space for solar | Sensible second metric: Heating system | Typical upgrade path : Fabric first (internal wall insulation), then air-source heat pump via BUS
- Property profile: Well-insulated 1980s semi, combi boiler, south-facing roof | Sensible second metric: Smart readiness | Typical upgrade path : Solar PV + battery + smart tariff; defer heat pump if fabric already strong
- Property profile: Flat, no roof, electric storage heaters | Sensible second metric: Heating system | Typical upgrade path : Likely heat pump or high-efficiency system; smart readiness may be unreachable , check exemption routes
- Property profile: Rural oil heating, large garden | Sensible second metric: Heating system | Typical upgrade path : £9,000 BUS grant + fabric upgrades
Plan the secondary metric before ordering works. Installing solar primarily for MEES only to discover you needed heating system band C wastes budget.
SAP-to-HEM transition: what assessors and owners should expect
Modular inputs replace RdSAP rigidity
Today's RdSAP is largely "all-or-nothing" , a fixed reduced dataset. HEM proposes a modular approach: assessors enter full detail where available and rely on validated defaults elsewhere. Over time this could allow multiple assessment tiers (desktop vs full survey).
Practical effect: future EPCs may better reflect recent upgrades (new windows, heat pump, solar) if the assessor captures them, reducing the gap between certificate and reality.
Dual-running period
Industry expects SAP and HEM to run in parallel for roughly 24 months after launch, similar to other building-regulation transitions. SAP 10.3 remains the bridge methodology during RdSAP 10 bedding-in. Exact dates will appear in the Summer 2026 implementation plan.
No live calculator yet
Government has published HEM reference code but no public calculator at consultation stage. You cannot yet model a HEM score for your property. Use current EPCs and professional surveys for planning in 2026.
Grants and funding during the transition
Current schemes still rely on today's EPC bands:
- Scheme: Warm Homes: Local Grant | EPC requirement (current): D–G for eligibility | HEM note : Legacy rating likely during transition
- Scheme: ECO4 | EPC requirement (current): Varies by route | HEM note : Ends 31 December 2026 , apply now
- Scheme: BUS | EPC requirement (current): Not EPC-gated directly | HEM note : Supports heating-system metric later
- Scheme: Landlord MEES | EPC requirement (current): E today; C by 2030 | HEM note : Dual-metric compliance from HEM era
Do not delay insulation or heating upgrades waiting for HEM. Eligible households should use free grant routes now; landlords should start spending against the £10,000 cap from October 2025.
Action checklist for landlords (2026–2027)
- Audit every EPC , note expiry dates; certificates lodged under SAP remain valid but may understate recent works.
- Pick your second metric per property , heating system vs smart readiness based on roof space, tenure and budget.
- Sequence fabric first , fabric performance is mandatory for MEES; heating and smart scores build on a sound thermal envelope.
- Log spend from October 2025 , invoices for insulation, heating, glazing, assessments and specialist advice count towards the £10,000 cap (except BUS).
- Watch for Summer 2026 plan , implementation dates, assessor training and software availability will firm up then.
- Commission new EPCs strategically , before 2030, a fresh assessment under HEM may give clearer dual-metric guidance than a ageing SAP certificate.
Action checklist for homeowners
- Check your current EPC on GOV.UK.
- If D–G and on low income, apply for Warm Homes: Local Grant via your council , do not wait for HEM.
- If upgrading heating, use current MCS installer quotes and BUS grants; future heating-system metric rewards heat pumps over direct electric.
- Consider solar and battery if south-facing roof space exists , supports smart readiness metric if you become a landlord later.
How this differs from our earlier HEM overview
We published a general Home Energy Model 2026 guide covering timelines and grant links. This article focuses on the dual-metric certificate structure and landlord compliance mechanics , the gap most competitor content now targets following the March 2026 methodology update.
Bottom line
The Home Energy Model replaces SAP/RdSAP from H2 2027, introducing four headline metrics plus a legacy A–G rating until end 2029. Landlords face band C on fabric plus either heating or smart readiness by October 2030, with up to £10,000 investment per property.
2026 is the window to plan metric choice, start qualifying works, and secure grant funding under today's rules. Waiting for the new certificate format risks compressed timelines and installer availability closer to the deadline.
Need help mapping a portfolio to dual-metric compliance? Contact Cucumber Eco for EPC assessment and retrofit planning.
