The government's consultation on using the Home Energy Model for existing dwelling EPCs is the single most important policy document for energy assessors in 2026. It proposes replacing RdSAP with a modular HEM-based methodology, introducing four new headline metrics, and fundamentally changing how 25 million existing homes are assessed. The consultation closes on 18 March 2026 — here is what it says, what industry bodies think, and how to have your say.
HEM EPC Consultation Deep Dive — Modular Inputs, Four Metrics, and a New Assessment Era
· Source: GOV.UK
What the consultation proposes
The consultation sets out how the Home Energy Model will be extended to assess existing dwellings and produce new-format EPCs. The core proposal is a modular input approach that replaces the rigid RdSAP methodology. Instead of a fixed reduced-data pathway, assessors will be able to enter detailed data where it is available (for example, from an installer's datasheet or a product label) and fall back to simplified defaults on a per-element basis where it is not.
The new EPCs will display four headline metrics instead of a single A–G rating: Fabric Performance, Heating System, Smart Readiness, and Energy Cost. Each metric except energy cost will be banded A–G. Properties with fossil fuel heating cannot achieve a C rating on the heating system metric — a deliberate policy lever to encourage decarbonisation.
Assessment time implications
Industry testing shows that a standard house type takes approximately 1 hour 40 minutes in HEM compared to roughly 20 minutes in SAP (excluding geometry and U-value calculations). The modular input approach should reduce this for existing dwelling assessments by allowing defaults, but the overall direction is clear: assessments will take significantly longer and require more detailed data collection. Assessors will need new data points including site altitude, hot water outlet specifications, detailed pipework lengths, and specific product make/model information.
Timeline
The government's proposed timeline targets launch in late 2026 alongside the new EPC format, with mandatory use from October 2029. During the transition period, assessors will be able to produce EPCs using either the existing RdSAP methodology or the new HEM-based approach. See our Timeline & Status page for the complete picture.
What this means: This consultation will shape how existing dwellings are assessed for years to come. Whether you are an assessor, architect, or energy consultant, responding before 18 March 2026 is essential. The modular input model is a significant improvement over RdSAP's rigidity, but the detail of how defaults are set will determine whether assessments are practical or punitive.
CIBSE Raises Concerns Over Consultation Process
· Source: CIBSE
The Chartered Institution of Building Services Engineers has raised concerns about the consultation process. CIBSE notes that the 8-week consultation period is tight given the complexity of the proposals, and highlights missing detail on training requirements, tooling readiness, and the future of the Product Characteristics Database (PCDB). The body calls for greater clarity on how assessors will be supported through the transition.
What this means: CIBSE's concerns echo what many assessors are thinking — the policy direction is right, but the practical detail on training and tools needs to follow quickly.
RIBA Backs HEM as “Fit for the Future”
· Source: RIBA
The Royal Institute of British Architects has welcomed the consultation, describing HEM as “fit for the future” and a significant improvement over SAP. RIBA particularly supports the half-hourly timestep approach, which it says will better reward good architectural design including orientation, form factor, and natural ventilation strategies. The body also backs the move to open-source development.
What this means: Architects should welcome HEM's ability to model design decisions that SAP could not capture. Good design will finally be reflected in the numbers.
Landlord EPC C by 2030: Dual Metric Rule Confirmed
· Source: GOV.UK
Under the new Minimum Energy Efficiency Standards (MEES) framework, privately rented homes must reach EPC C by October 2030. The Warm Homes Plan confirms a dual metric rule: landlords must achieve a C rating on Fabric Performance plus at least one of Heating System or Smart Readiness. A £10,000 cost cap applies — landlords are not required to spend more than this per property.
What this means: The dual metric approach prevents landlords from simply installing a heat pump without addressing fabric. See our EPC changes guide for what this means for tenants and property owners.
UK Heat Pump Sales Hit Record 98,000 in 2024
· Source: Heat Pump Association
UK heat pump sales reached a record 98,000 units in 2024, a 56% year-on-year increase from 63,000 in 2023. The UK has bucked the European trend, where several markets saw declining sales. The BUS grant (£7,500 for heat pumps) and the approaching Future Homes Standard are credited as key drivers. Industry forecasts suggest the market could pass 150,000 units in 2025, with the FHS expected to push annual installations beyond 300,000.
What this means: The supply chain is scaling. For developers and builders, early procurement agreements remain important as demand accelerates toward the FHS deadline.
Building Safety Levy Starts October 2026
· Source: Browne Jacobson
The Building Safety Levy will apply to all new residential buildings from 1 October 2026. Current estimates suggest a charge of approximately £3,000 per plot, though final rates will vary by region and building type. Building control applications submitted before October 2026 will not be subject to the levy, creating an incentive for developers to advance their applications before the deadline.
What this means: Combined with the FHS transitional arrangements, developers face a double deadline in late 2026. Pipeline planning is critical.
Background & Context
The HEM EPC consultation sits within a broader transformation of UK energy performance policy. The government is simultaneously progressing the Future Homes Standard for new builds (expected December 2026), reforming the EPC framework to display four metrics instead of one, and extending HEM to cover the 25 million existing homes currently assessed under RdSAP. These three workstreams are converging on a single calculation engine — HEM — delivered through the centralised ECaaS platform.
For existing dwellings, the shift from RdSAP to HEM is transformative. RdSAP has served as the reduced-data pathway since 2005, using a fixed set of inputs and standardised assumptions. The new modular approach gives assessors flexibility to improve accuracy where data is available, while still allowing simplified defaults for elements that cannot be easily inspected. This is a pragmatic middle ground between the rigidity of RdSAP and the full data demands of a complete HEM assessment. Read our RdSAP Transition guide for the technical detail.
The consultation also raises important questions about the Product Characteristics Database (PCDB) and how product-specific data will feed into assessments. CIBSE and other industry bodies have highlighted that without a clear plan for PCDB reform, the modular input approach risks being undermined by a lack of reliable product data.
How to Respond to the Consultation
The consultation is open to anyone with an interest in how existing homes are assessed. You do not need to answer every question — partial responses are welcome. Here is how to get involved:
Where to respond
Submit your response through the official GOV.UK consultation page. The deadline is 18 March 2026.
Key questions to consider
- Are the proposed modular input levels appropriate? Should more or fewer elements allow simplified defaults?
- Is the transition timeline realistic given current assessor capacity and training infrastructure?
- How should the PCDB be reformed to support the modular input approach?
- What training and support will assessors need to deliver HEM-based assessments effectively?
- Are the four proposed EPC metrics clear and useful for homeowners and landlords?
Tips for a strong response
Draw on your practical experience. The government values real-world insight from practitioners over theoretical arguments. If you are an assessor, explain how the proposals would affect your day-to-day work. If you are a developer or builder, describe how the new EPC format would influence your decisions. Specific examples carry more weight than general statements.
Frequently Asked Questions
When does the HEM EPC consultation close?
The consultation closes on 18 March 2026. Responses must be submitted through the GOV.UK consultation page. It opened on 21 January 2026 and covers the proposed methodology for using HEM to assess existing dwellings and produce new-format EPCs.
What does the HEM EPC consultation propose?
The consultation proposes replacing RdSAP with the Home Energy Model for assessing existing dwellings. Key proposals include a modular input approach (detailed data where available, simplified defaults otherwise), four new headline EPC metrics, and a timeline targeting launch in late 2026 with mandatory use from October 2029.
Who should respond to the HEM EPC consultation?
Anyone working in energy assessment, property, or construction should consider responding. SAP assessors are most directly affected as the proposals will change how they assess existing dwellings. Architects, developers, builders, landlords, and energy consultants all have a stake. CIBSE and RIBA have published responses that can help inform individual submissions.
Related Pages
RdSAP Transition
How the shift from RdSAP to HEM will work for existing dwelling assessments.
New EPC Metrics
The four new headline metrics replacing the single A–G EPC rating.
HEM for SAP Assessors
What the transition to HEM means for your practice and qualifications.
Timeline & Status
Live tracker of HEM, FHS, and EPC reform milestones.