The HNMBR (Heat Network (Metering and Billing) Regulations) were first implemented in 2014. The Regulations are mandatory and enforced by the Office for Product Safety and Standards (OPSS), part of the Department for Energy, Security and Net Zero (DESNZ). The main purpose of the HNMBR is to increase energy efficiency and decrease carbon emissions from heating throughout the UK, with a large focus on domestic and commercial tenanted buildings.  The Regulations focus on the metering and billing of heat networks and are applicable to the majority of district and communal heat networks throughout England, Scotland, Wales and Northern Ireland. This covers most networks in the residential, commercial, industrial, and public sectors.