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 Networks (Market Framework) Regulations 2025, heat network operators must meet Ofgem's authorisation conditions. The Heat Network Technical Assurance Scheme (HNTAS) is in development, with a planned launch in 2027, and will introduce mandatory technical performance standards. Proper HIU commissioning is fundamental to achieving low return temperatures and supporting compliance with Ofgem's authorisation conditions.
Each heat interface unit commissioning record should capture the property address, HIU make and model, heat meter serial number, commissioning date and engineer, flow and return temperature settings, and differential pressure settings. See our full guide to HIU commissioning requirements and records.
Heat network operators must meet Ofgem's authorisation conditions under Section C and metering obligations under Section B. Deficiencies in HIU and metering records are a compliance risk. Read more about Ofgem requirements for HIU and metering 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. Heat network registration is open with a deadline of 26 January 2027. This tool helps operators demonstrate compliance through proper HIU commissioning documentation.