Heat Network Technical Assurance Scheme - All Networks Must Comply
NO Minimum Capacity Threshold | Applies to ALL Heat Networks
What is HNTAS?
The Heat Network Technical Assurance Scheme (HNTAS) is a performance-based regulatory scheme that ensures all heat networks in Great Britain meet minimum technical standards for performance, reliability, and consumer protection.
⚠️ Universal Application: HNTAS applies to ALL heat networks - from small communal systems to large city-wide district heating. There is NO minimum capacity threshold. Every heat network must comply, regardless of size.
Who Must Comply?
All heat networks including:
Communal heating systems (even single buildings with shared heating)
Note: The pathway your network follows depends on whether it's NEW (not yet operational) or EXISTING (already serving customers). Network size does NOT determine the pathway.
Determine Your Compliance Pathway
Answer these questions to identify which HNTAS pathway applies to your heat network
🏗️
New Build
Design, construction, or commissioning stage
🏢
Existing Network
Already operational and serving customers
New Build Network: 8-Stage Assessment Process
New build heat networks must pass independent assessments at key gateways throughout their lifecycle. This prevents performance issues being designed or built into the network.
Important: You cannot proceed past a gateway until you have passed the required assessment. Plan for assessment time in your project schedule.
PHASE 1: FEASIBILITY
Stage 1: Concept Design
Required Assessment Point
Initial network design assessed for compliance with TS1 technical requirements. Assessor reviews:
Proposed heat source and capacity
Distribution network routing
Energy centre location and space requirements
Preliminary heat loss calculations
Consumer connection strategy
🚪 GATEWAY 1: Design Approval to Proceed
Pass Stage 1 assessment before progressing to detailed design
PHASE 2: DESIGN
Stage 2: Developed Design
Optional Assessment Point
Detailed design review - optional but recommended for complex networks. Covers:
Detailed hydraulic modeling
Equipment specifications
Control philosophy
Metering strategy
Stage 3: Technical Design
Required Assessment Point
Final design freeze assessment before construction. Assessor verifies:
Compliance with all TS1 technical specifications
Pipe sizing and insulation standards
Flow and return temperature design
HIU specifications and performance
Metering and monitoring provisions
Quality assurance procedures for construction
🚪 GATEWAY 2: Construction Approval
Pass Stage 3 assessment before starting construction
PHASE 3: CONSTRUCTION
Stage 4: Construction Design
Required Assessment Point
Assessment of construction-ready documentation and site preparations:
Final construction drawings
Material specifications and certifications
Installation procedures
Site quality controls
Stage 5: Installation
Required Assessment Point
On-site inspection during construction phase. Assessor conducts:
Pass Stage 6 assessment to receive provisional HNTAS certificate and begin operations
PHASE 4: INITIAL OPERATION (First 2 Years)
Stage 7: Operation & Maintenance
Required Assessment Point - After 2 Years Operation
Operational performance assessment based on actual data. Assessor reviews:
24 months of operational performance data
Actual vs predicted heat losses
System efficiency metrics
Reliability and uptime statistics
Consumer complaints and resolution
Maintenance records and practices
🏆 GATEWAY 4: FULL HNTAS CERTIFICATION
Pass Stage 7 assessment to receive full HNTAS certification
PHASE 5: ONGOING OPERATION
Stage 8: Ongoing Monitoring
Continuous Requirement
After certification, heat network operators must:
Submit performance data to HNTAS digital portal regularly
Maintain compliance with key performance indicators
Notify of any significant changes or incidents
Undergo periodic reassessment (frequency TBC)
Existing Networks: Milestone-Based Compliance
Existing heat networks follow a different pathway with progressive milestones. This recognizes that existing networks may need time to install metering, improve performance, and gather operational data.
Transition Period: Existing networks will have a significant transition period to install required metering and achieve performance thresholds. Final thresholds will be set at more permissive levels than new builds.
Heat loss limits (more permissive than new builds)
System efficiency
Reliability and uptime
Temperature control
Submit initial performance data to HNTAS portal
Purpose: Establish baseline performance and identify networks requiring improvement
Milestone 3A: Performance Improvement Plans
Timeline: For networks not meeting Milestone 2 thresholds
Requirements:
Conduct detailed performance audit
Identify root causes of underperformance
Develop costed improvement plan with timeline
Submit plan to assessor for approval
Implement approved improvements
Demonstrate improved performance
Purpose: Bring underperforming networks up to minimum standards
Milestone 3B: Enhanced Metering & Monitoring
Timeline: For networks initially exempt from M2 metering requirements
Requirements:
Install comprehensive metering at:
Heat source output
Distribution network key points
Consumer connection points (HIUs)
Implement remote monitoring systems
Establish data collection and reporting procedures
Integrate with HNTAS digital portal
Purpose: Ensure all networks have adequate monitoring to prove ongoing compliance
Milestone 4: Achieve HNTAS Certification
Timeline: After completing M2, M3A (if applicable), and M3B
Requirements:
Demonstrate sustained compliance with performance thresholds
Provide evidence of:
12 months minimum of operational data
Proper maintenance procedures
Competent operator in place
Consumer protection measures
Incident response protocols
Pass independent assessment
Receive HNTAS certificate
Purpose: Final certification that network meets all HNTAS requirements
Post-Certification: Once certified, existing networks must continue submitting performance data to the HNTAS digital portal and maintain compliance with key performance indicators, just like new build networks.
HNTAS Readiness Checklist
Complete this assessment to determine your heat network's readiness for HNTAS compliance
Documentation & Planning
Metering & Monitoring
Technical Compliance
Assessment Preparation
Readiness Score
0 / 16 (0%)
Key Changes from Previous Guidance
Important Clarifications:
NO minimum capacity threshold - Earlier assumptions about 500kW or 1MW minimums are incorrect
NO phased rollout by size - The pathway is determined by whether network is new or existing, not by capacity
All communal systems included - Even single buildings with shared heating must comply
Timeline is pathway-specific - New builds assessed during construction; existing networks follow milestones
Governance Structure
Ofgem - Heat network regulator (under Energy Act 2023)
Code Manager - Licensed by Ofgem to maintain:
Technical Specifications (what networks must comply with)
Assessment Procedures (how compliance is demonstrated)
Assessor Requirements (who can assess compliance)
Scheme Operator - Day-to-day operation of HNTAS (may be outsourced by Code Manager)
Registered Assessors - Conduct HNTAS assessments at required stages
Certification Bodies - Issue HNTAS certificates following successful assessments
Does my small communal system really need to comply?
Yes. HNTAS applies to ALL heat networks regardless of size - from small communal systems in single buildings to large district schemes. There is no minimum capacity threshold.
When does HNTAS become mandatory?
The scheme is being phased in following completion of pilot programmes. Specific implementation dates will be announced following final regulations. New builds should plan for HNTAS now; existing networks will have transition periods.
How much will HNTAS assessment cost?
Assessment fees will vary based on network size and complexity. Typical ranges: £8,000-£25,000 for full new build assessment through all stages. Existing network milestone assessments may be less.
Can I use CP1 (2020) compliance to meet HNTAS?
CP1 (2020) provides a good foundation, but TS1 introduces new requirements in several areas. Networks designed to CP1 will be well-prepared but must verify compliance against TS1 specifically.
What happens if my existing network can't meet performance thresholds?
You'll develop a Performance Improvement Plan (Milestone 3A) with timeline and budget for upgrades. Thresholds for existing networks are more permissive than new builds, recognizing retrofit challenges.
Who can be a HNTAS assessor?
Assessors must be registered by the Code Manager and meet specific competency requirements. Training is available through the BESA Shadow Training Provider.