Guidance

HNTAS: Existing heat networks - draft assessment procedures for Milestone 3B

Draft procedures that Heat Network Technical Assurance Scheme (HNTAS) registered assessors will need to follow to assess a heat network’s compliance with HNTAS technical requirements.

• From: Department for Energy Security and Net Zero
• Published: 5 January 2026

Applies to England, Scotland and Wales

Documents

DRAFT: HNTAS existing heat network assessment procedure Milestone 3B - Consumer Connections

Ref: HNTAS-EX-AP-CC-M3B

PDF, 296 KB, 14 pages

Details

This draft assessment procedure for existing heat networks details the activities to be undertaken to verify compliance with Milestone 3B requirements in the upcoming Heat Network Technical Assurance Scheme (HNTAS).  

Milestone 3B sets out metering and monitoring requirements for existing networks which were not previously required to have metering installed under Heat Network Metering and Billing Regulations (HNMBR) 2014.

Milestone 3B only applies to the consumer connection element.

The document is for use by:

• heat network assessors
• heat network operators

This assessment procedure corresponds to the draft HNTAS technical specification for Milestone 3B.

Next steps

We will be requesting feedback on the information in these documents. We will run a change management process in parallel with the HNTAS technical standards consultation which will launch shortly.

We will make final versions of these documents available before the scheme starts.

Published 5 January 2026