The HIU Commissioning Tool is a digital commissioning platform for Heat Interface Units (HIUs) on UK heat networks. It enables engineers to follow standardised CIBSE CP1 test procedures, generate digital commissioning certificates, and track VWART (Volume Weighted Average Return Temperature) performance across entire networks.
Poorly commissioned HIUs are the leading cause of high return temperatures and network inefficiency on district heating systems. Under the Heat Network Technical Assurance Scheme (HNTAS), heat networks must demonstrate performance compliance to meet Ofgem authorisation requirements. Proper HIU commissioning is fundamental to meeting HNTAS key performance indicators and ensuring heat network compliance.
The HIU Commissioning Tool serves heat network engineers, commissioning contractors, M&E consultants, heat network operators, housing associations, and facilities managers responsible for HIU performance across their portfolio. Whether commissioning a single unit or managing a fleet of hundreds, the tool provides the structure and compliance documentation needed.
The Energy Act 2023 established Ofgem as the regulator for UK heat networks. The Heat Networks (Market Framework) Regulations 2025 commenced on 27 January 2026, with Ofgem authorisation now required for heat network operators. The HNTAS consultation closes 15 April 2026, and heat network registration opens Spring 2026 with a deadline of January 2027. This tool helps operators demonstrate compliance with these requirements through proper HIU commissioning documentation.
The tool captures and validates key performance indicators required by HNTAS, including CC-KPI-09, CC-KPI-10, CC-KPI-11, CC-KPI-12, CC-KPI-13, and commissioning items 6.4.2 through 6.4.9. Each measurement is validated against site-specific design parameters to ensure compliance with heat network performance standards.
For operators who need to calculate compliant heat tariffs aligned with Ofgem Authorisation Conditions A7 and A8, our free Tariff Calculator models all cost components including fuel, operation and maintenance, network losses, metering, and a fair return on capital — producing a pence-per-kWh standing charge and unit rate that meets Ofgem's transparency requirements.