Guidance

Heat Network Technical Assurance Scheme (HNTAS)

Updated 21 January 2026

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This publication is available at https://www.gov.uk/government/publications/heat-networks-regulation-technical-standards/heat-network-technical-assurance-scheme-hntas

The Energy Act 2023 provides the powers for government to mandate heat network technical standards in Great Britain through regulations. We are introducing regulatory technical requirements and a Heat Network Technical Assurance Scheme (HNTAS) to help heat network operators demonstrate compliance with these requirements. HNTAS will be phased in over time, with a planned launch in 2027, once policy proposals are consulted on and finalised. This is to ensure the sector has sufficient time to shape, understand and comply with the scheme.

The Heat Network Technical Standards consultation is live and closes on 15 April 2026.

1. Overview of HNTAS

Since the end of 2022 DESNZ has been working with its Technical Author (FairHeat) to develop a technical standards Code. This sets out technical requirements (e.g. pipe insulation, water flow temperatures) which will be mandated in upcoming regulation. Many of these technical requirements build on the voluntary standards set out in CIBSE CP1 (2020). DESNZ and FairHeat have also been developing a scheme of assessment and certification to ensure heat network compliance with these technical requirements can be demonstrated. Together, these requirements and assurance processes form the Heat Network Technical Assurance Scheme (HNTAS).

Technical standards regulation will apply to heat networks from communal to city wide district systems, including both new build and existing networks.

2. Objectives and principles

HNTAS is being designed with deliverability and proportionality as two of its leading principles. Specifically, we are keen to ensure that the introduction of HNTAS does not place undue burden or cost on heat network operators or heat network consumers.

HNTAS will enhance the transparency of heat network performance, and strengthen accountability for parties engaged in the planning, construction, management, and maintenance of heat networks. As a result, HNTAS has the potential to reduce carbon emissions by making heat networks more efficient, reduce capital and operational costs, and improve consumer experience.

Scheme objectives and core principles

Vision

Enable low-emissions, reliable and affordable heat to be delivered to UK communities via heat networks.

Aim

Develop a heat network technical assurance scheme that ensures a minimum level of performance and reliability for heat networks in the UK.

Objectives

  • Reduce carbon emissions and cost of heat by making heat networks more efficient
  • Improve affordability by reducing capital and operational costs
  • Improve consumer experience with improved reliability and quality of heat supplied
  • Improve reputation and investor confidence in heat networks
  • Build evidence through better data collection and reporting on technical quality

Core principles

  • Outcomes orientated
  • Preventative
  • Proportionate
  • Deliverable
  • Adaptable
  • Enforceable

HNTAS will be a performance-based assurance scheme which applies to different identifiable elements (such as energy centre, district distribution network, communal distribution network) of a heat network. For each element, assessments against minimum standards are made in various lifecycle stages of a heat network. In the design and construction stages, assessments will be made to validate the claims that certain performance outcomes will be achieved. Upon commissioning, assessments will verify that performance outcomes have been achieved and maintained.

3. How compliance will be demonstrated

Under HNTAS, heat networks will be required to pass assessments to demonstrate that they have achieved the mandated minimum technical standards.

3.1 New build networks

For new build networks an assessment pass will be required at 3 key points in a heat network’s lifecycle:

  • before a network is allowed to start design
  • before starting construction
  • before starting operation

An assessment pass will also be required after 2 years of operation to ensure that performance levels continue to meet requirements.

HNTAS Assurance Process

HNTAS Phase 1: Feasibility

  • Stage 1 - Concept design (required HNTAS stage - assessment point)

Gateway 1

HNTAS Phase 2: Design

  • Stage 2 - Developed design (optional HNTAS Stage - assessment point)
  • Stage 3 - Technical design (required HNTAS stage - assessment point)

Gateway 2

HNTAS Phase 3: Construction

  • Stage 4 - Construction design (required HNTAS stage - assessment point)
  • Stage 5 - Installation (required HNTAS stage - assessment point)
  • Stage 6 - Commissioning (required HNTAS stage - assessment point)

Gateway 3 - Certification Point

HNTAS Phase 4: Operation (initial 2 years)

  • Stage 7 - Operation and maintenance (required HNTAS stage - assessment point)

Gateway 4 - Certification Point

HNTAS Phase 5: Operation (ongoing)

  • Stage 8 - Ongoing monitoring

3.2 Existing networks

For existing networks, assessments will be required after a set period to ensure performance levels meet requirements. The existing stock of communal and district heat networks will also have a significant transition period to get the right metering in place, to be able to prove performance. Final performance thresholds will be set at a more permissive level for existing networks and these networks will be given time to reach these.

3.3 After achieving HNTAS certification

For both new and existing networks, assessment passes will enable a network to be awarded a HNTAS certificate as evidence of compliance with HNTAS.

Once a network achieves HNTAS certification, the heat network operator will be required to regularly submit data to a HNTAS digital portal to show they continue to meet HNTAS key performance indicators.

4. Governance structure

As provided by the Energy Act 2023, Ofgem will be the regulator of heat networks. The Energy Act also provides for  a heat network Code Manager to maintain the Code documents which will include the:

1. Technical specifications (what heat networks must comply with)
2. Assurance procedures (how compliance is demonstrated)
3. Assessor requirements (who can assess compliance)
4. Certifier requirements (who can certify compliance)

The Code Manager may outsource the day-to-day operation of HNTAS to a Scheme Operator.

It is expected that assessors will be registered by the Code Manager to carry out HNTAS assessments. We anticipate that a Certification Body which employs certifiers will also need to be registered by the Code Manager to deliver certification activities.

5. CIBSE CP1: Heat networks: Code of Practice for the UK

CP1 (2020), published by the Chartered Institution of Building Services Engineers (CIBSE), is the recognised Code of Practice for heat networks in the UK. It contains technical guidance and sets out voluntary minimum standards for UK heat networks. Having most recently been updated in 2020, CP1 will be the basis for the minimum regulatory standards used within HNTAS.

CP1 (2020) will not be an exact representation of HNTAS standards, but it does give a very good starting point in that CP1 (2020) compliant networks will be very well prepared for forthcoming regulatory technical standards. Until recently it has only been free to CIBSE members, but a partnership between CIBSE and DESNZ has now removed the paywall to make CP1 (2020) free-to-all:

6. TS1 – The Heat Network Technical Standard

DESNZ has been working with technical author FairHeat and a wide range of industry stakeholders to develop TS1 – the Heat Network Technical Standard. This document will supersede the Heat Networks: Code of Practice for the UK (CP1). It is largely based on the content from CP1 (2020), but transitions from a code of practice to a formal standard and introduces new requirements in several key technical areas. TS1 will serve as the principal reference point for HNTAS, supporting the sector’s move to regulation by providing robust technical standards to ensure high performance and good consumer outcomes.

TS1 is available in a draft format due to its interaction with other HNTAS documentation. The final version of this document will be released before the launch of HNTAS.

7. Draft Code documents  

We published the Technical Specifications and Assessment Procedures for new build networks in December 2025 and for existing networks in January 2026. Developed in collaboration with industry, we have released these in draft form ahead of the scheme’s planned launch, to help the sector become familiar with proposed HNTAS requirements.

Technical Specifications - these Technical Specifications detail the technical obligations to be fulfilled as part of the scheme including the:

  • technical requirements to be met
  • performance monitoring requirements to be met
  • key failures to be avoided
  • evidence requirements to be provided to demonstrate conformity with HNTAS

For existing heat networks, Technical Specifications are structured by Milestones that networks must meet after a period of time.

  • Milestone 2 – Minimum performance and reliability thresholds, including metering and monitoring requirements
  • Milestone 3A – Performance Improvement Plans
  • Milestone 3B – Metering and monitoring requirements for networks not required to meet these at Milestone 2
  • Milestone 4 – Requirements for achieving HNTAS Certification

Assessment Procedures - these Assessment Procedures detail the assessment activities to be undertaken to provide assurance that the obligations in the Technical Specifications are fulfilled. There is an Assessment Procedures document associated with each Technical Specification.

8. HNTAS pilot programme

We have undertaken a pilot programme to test the technical requirements and assurance processes on real networks to make sure they work in practice.

The first wave of the programme, which included eleven new build pilots, has now concluded. The pilot projects spanned various heat network types and stages to gather comprehensive insights. Six Assessor Organisations were appointed to evaluate these projects and were trained in HNTAS assessment processes. Duty holders of the heat network pilot projects also received HNTAS training to enable them to participate in the programme. The Key Findings report, which will be available shortly, outlines how the scheme has been refined in response to pilot insights, with improvements focused on enhancing proportionality and usability.

We have also undertaken piloting of draft HNTAS requirements on existing networks. The lessons learned will help ensure HNTAS works in practice and aligns with industry needs.

9. Stakeholder engagement and consultation 

Stakeholder engagement has been key in developing  HNTAS. Multiple technical workshops have been held to gather ideas and expertise from manufacturers, housing associations, local authorities, consultancies, developers, contractors, energy service companies, trade associations, and professional bodies.  

The outputs of these workshops have been used to inform the draft Code documents, TS1 and a new Metering and Monitoring Standard. Together these documents outline the technical requirements of the scheme and how compliance can be demonstrated. In addition to testing the draft scheme through the HNTAS Pilot Programme, we will also be welcoming views on the requirements within the draft Code documents, the draft Metering and Monitoring Standard and the draft TS1 via a Technical Feedback Process in due course. The Technical Feedback Process will run as a parallel process to the policy consultation and is aimed towards stakeholders that have a technical understanding of heat networks.

10. HNTAS training courses

The Building Engineering Services Association (BESA) has been appointed to the role of HNTAS Shadow Training Provider, to develop and deliver HNTAS training courses. The first HNTAS courses are now live and available to book:

- Training Hub

Stakeholders have regularly raised the importance of setting up and delivering high quality training courses to prepare the market for regulation. We anticipate that HNTAS will introduce several new roles and create new job opportunities for the sector. Many of the Shadow Training Provider’s HNTAS courses will need to be attended by organisations and individuals before they will be able to fulfil these roles. The Training Provider is ‘shadow’ as they will be active before HNTAS launches.

The courses delivered will work towards achieving accreditation, which will ensure delegates receive high quality training and can perform key HNTAS roles to a high standard. Many courses will become available in 2026.

11. News updates and reference materials

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