For many years, the CP1 Heat Networks Code of Practice shaped how heat networks were designed, delivered and operated across the UK. It brought structure to a growing sector and helped establish a shared understanding of what good looks like in practice.
However, CP1 has always been voluntary. While it is widely referenced and frequently written into briefs and funding conditions, it is not a statutory technical standard. As heat networks move into a regulated environment, that distinction becomes increasingly important.
Draft Heat Network Technical Standard TS1 represents the next stage in the sector’s development. It is intended to move heat networks from voluntary alignment towards assessed technical compliance through the Heat Network Technical Assurance Scheme.
As consultants working across heat network feasibility, design, commissioning and assurance, we see first-hand how voluntary standards translate into real-world delivery, and where gaps most often emerge. Below, we set CP1 in context before focusing on what TS1 introduces and why it matters in practice.
What CP1 was and why it mattered
CP1 was first published in 2015 and updated in 2020. Its purpose was to create a common framework for the design, delivery and operation of heat networks across the full lifecycle, at a time when expectations varied widely between projects.
CP1 addressed inconsistency by defining lifecycle stages and setting out clear outputs that project teams could use in briefs, procurement, commissioning plans and operational records. It also embedded performance themes that directly influence efficiency and customer experience.
These themes included:
- Designing for low return temperatures
- Minimising heat losses through routing and insulation
- Right-sizing plant and distribution networks
- Treating commissioning as a performance check rather than a paperwork exercise
- Linking technical decisions to outcomes that customers actually feel
Where CP1 was applied rigorously, it improved consistency and long-term performance. However, compliance relied on voluntary adoption and interpretation. In practice, this meant that two schemes could both claim CP1 alignment while delivering very different operational outcomes.
For those wishing to refer directly to the source document, the CP1 Heat Networks: Code of Practice for the UK (2020 edition) sets out the technical framework that shaped much of the sector’s approach over the last decade.
What is Heat Network Technical Standard TS1?
TS1 is a draft technical standard published by the Department for Energy Security and Net Zero. Its purpose is to define minimum technical requirements for heat networks rather than recommended best practice.
Unlike CP1, TS1 is written with assessment in mind. It is designed to sit alongside HNTAS, enabling independent technical review based on documented evidence rather than narrative alignment. The government’s guidance on the Heat Network Technical Standard TS1 explains how the draft standard is intended to support future regulation and technical assurance.
At its core, TS1 focuses on three questions:
- What must the heat network achieve
- How is that achievement demonstrated
- Who is accountable for the evidence
TS1 builds on the lifecycle thinking introduced by CP1 but reduces ambiguity so that requirements can be assessed consistently. While TS1 is currently published in draft form, its structure and intent provide a clear indication of the direction of travel for technical regulation and assurance.
How TS1 is structured
TS1 spans the full lifecycle of a heat network, from design and installation through to commissioning, operation and customer outcomes. The scope will feel familiar to anyone who has worked with CP1.
The difference lies in emphasis. TS1 places greater weight on:
- Defined technical requirements rather than descriptive guidance
- Measurable criteria rather than narrative intent
- Evidence and records rather than assumptions
This structure supports assurance and, ultimately, regulation.
CP1 and TS1 compared
Although TS1 is largely based on the 2020 edition of CP1, the way requirements are framed differs.
| Area | CP1 Code of Practice | TS1 Technical Standard |
| Status | Voluntary guidance | Draft minimum technical standard |
| Purpose | Promote best practice | Define assessable requirements |
| Focus | Lifecycle outputs and themes | Evidence-led compliance |
| Compliance | Often self-declared | Intended to be independently assessed |
| Interpretation | High flexibility | Reduced ambiguity |
The practical implication of this shift is that compliance under TS1 must be demonstrable to a third party, rather than inferred from design intent alone.
What TS1 changes in practice
In practice, the most significant changes we see under TS1 are not about new engineering principles, but about how projects are structured, managed and evidenced from the outset.
Procurement language becomes more precise
Under voluntary guidance, phrases such as “comply with CP1 where practicable” are common. Under an assurance model, this creates uncertainty.
TS1 encourages clearer requirements. Clients need to ask for defined outcomes and the evidence that will demonstrate them, rather than relying on broad statements of intent.
Commissioning becomes the proof point
Both CP1 and TS1 recognise commissioning as critical, but TS1 raises its status. Commissioning is where compliance is demonstrated, not simply where systems are switched on.
Low return temperatures are a clear example. Under TS1, they are not just a design aim. They must be evidenced through measured results, recorded setpoints and repeatable tests.
Evidence is planned from the outset
TS1 readiness is less about producing more documents and more about structuring information properly.
Design assumptions, calculations, commissioning results, control strategies and asset data need to form a coherent, traceable record. When evidence is captured as the project progresses, assurance becomes far less disruptive, particularly at commissioning and handover, where missing records often cause delays.
Moving from CP1 toTS1
Based on our work supporting heat network projects through feasibility, design, commissioning and handover, preparing for TS1 involves four practical steps.
Step 1: Map existing practice to TS1 requirements
List the CP1 outputs already used in briefs, specifications and commissioning plans, then map them against TS1 requirements to identify gaps early.
Step 2: Strengthen proof, not paperwork
Focus on evidence that a third party can follow without interpretation, such as commissioning test results linked to target values, recorded control strategies, representative temperature data and signed acceptance records.
Step 3: Build an assurance-ready handover pack
Create a clear structure from day one covering design basis, calculations, commissioning results, operation and maintenance information, and customer guidance.
Step 4: Assign clear ownership
Assurance depends on accountability. Assign a named role responsible for evidence completeness, version control and sign-off.
Early-stage design plays a critical role, and our design services ensure heat networks are structured from the outset to meet TS1 requirements and support successful HNTAS compliance, rather than relying on corrective measures later.
This is where independent technical support often adds the most value. Our handover and commissioning services for heat networks are designed to verify performance against defined standards and support teams preparing for TS1 and HNTAS-style assessment. Early engagement at this stage typically reduces rework and late-stage risk.
Where CP1 still fits
CP1 remains a useful reference. Its structure and language continue to support good design and project management, and many teams will still use it as a practical tool.
What has changed is the destination. CP1 helped the sector improve. TS1 is intended to support more consistent and transparent demonstration of compliance as regulation is introduced.
For organisations planning new schemes or upgrades, this shift also aligns closely with funding and improvement mechanisms such as the Green Heat Network Fund and the Heat Network Efficiency Scheme, where robust technical evidence and long-term performance assurance are increasingly important.
Note: Heat Network Technical Standard TS1 is currently published in draft form and may be updated as the regulation is finalised. This article is intended to provide technical context and industry insight rather than formal legal or regulatory advice. Project-specific requirements should always be confirmed against the latest published guidance and relevant scheme conditions.
Conclusion
The move from CP1 to TS1 is not about reinventing heat network design. It is about moving from voluntary guidance to assured delivery.
The practical takeaway from this shift is clear: projects that treat evidence, accountability and performance verification as core delivery requirements are better positioned for assurance, regulation and long-term operation.