HNTAS: what is proposed, what is not decided, and what to do now

What HNTAS would be

A scheme that “will set the technical requirements that new and existing heat networks need to meet, alongside an assessment and certification process”.

• Legal basis. The scheme documents would be designated under the Energy Act by a future piece of secondary legislation, which makes the requirements in them legal obligations for those in scope.
• Who runs it. DESNZ proposes to carry out the Code Manager function itself, at least at first, with a single Certification Body, a Training Provider and a Scheme Operator at commencement.
• Ofgem’s part. Ofgem would monitor compliance with the authorisation conditions; signing up to HNTAS would itself become a condition of authorisation for networks in scope.

Who it would apply to

• New heat networks and “the c12,000 existing heat networks across Great Britain”.
• The operator: “the operator would also be the entity required to meet the new technical standards”.
• Size thresholds are proposed: no new network below six properties, or the equivalent capacity, and 450kW for existing and 225kW for new non-domestic or mixed networks. The threshold for existing domestic networks is still being consulted on, with eleven or more properties as one option.
• Industrial sites would be excluded at launch.

What it would require

• Assessment across the network’s life, in eight stages from concept design to ongoing monitoring. Passing an assessment earns a Statement of Conformity.
• Two certificates: the first after commissioning and before customers are supplied, the second after two years of operation.
• Certification before authorisation for new networks: passing HNTAS assessments and certification would be a prerequisite for becoming authorised.
• A phased route for existing networks, registering in the first year and reaching certification several years later, on a timetable that depends on their metering.
• Performance and metering targets, including heat losses of no more than 400 W per dwelling at the second milestone and 200 W per dwelling for certification, and heat meters to at least the equivalent of MID Class 2 accuracy.
• TS1, the Heat Network Technical Standard that replaces CP1 (2020), as the most heavily referenced standard. The draft was published on 18 November 2025 (gov.uk).

What is not yet decided

• The detailed technical requirements: the consultation “focuses on the overall design of the scheme rather than the detailed technical requirements”.
• How far the scheme reaches into existing networks, including an option to stop at the second milestone rather than require full certification.
• The five-year deadline for metering.
• The longer-term governance of the Code Manager, and any financial or non-financial incentives.

What to do now

Register with Ofgem. Ofgem registration is not intended to depend on HNTAS. Existing networks must be registered on or before 26 January 2027: how to register.

From the consultation. Operators “should look to improve their networks at the earliest possible point and ahead of these deadlines”, and some parts of the scheme may open for voluntary engagement before regulation.

Our suggestions, which the consultation does not set out itself:

• Find out what metering each network has, since that sets its proposed timetable.
• Start keeping operational data, including heat losses, and check the accuracy class of your meters.
• For schemes in development, record the planning and M&E contract status, which the proposals use to decide their route.

Common questions