UNC Review Group 0251 Metering Issue for Consideration 21 September 2009

Metering - Governance Background Metering is Governed by DECC and Ofgem Responsibility is at the terminals Regulation provide prescriptive arrangements (GCOTE 1997) Metering predominately Orifice plates (120 / 60) Purpose for metering developed

Ofgem Governance Provided for within the GCOTE Scope for CV and metering Requires sites to be directed, setting out performance requirements and Letter of approval Charging areas defined by industry Declared or FWACV can be operated FWACV seeks to protect consumers (1MJ/m^3 c2.5%)

Metering Standards Orifice plates standard ISO 5167 UNC OAD appendix D sets out requirements 1.1 % on volume Disconnect between entry and exit 1991 Vs 2003 Supplementary agreements allow greater uncertainty ? 0 to 30% of flow, +/- 3.6% 30 to 100 % of flow, +/- 2.1%

ISO 5167 ISO standards updated approximately every 5 years Changes to ISO 5167 – 2003 1. Discharge Coefficient 2. Expansibility Factor 3. Permanent Pressure Loss 4. Upstream Temperature Considered that 1991 overstates when compared to 2003 by approximately 1%, depending upon meter configuration

Other Factors and consideration Fixed factors for Pressure Temperature http://www.ofgem.gov.uk/Networks/Archive/Gas%20energy%20measurement%20a%20consultation%20document%2027%2012.pdf

Moving the debate forward To what extent does the difference in standards and range of uncertainty contribute to shrinkage Winners and losers Are localised factors more applicable Offtake Consumers meters This is an area for further work and investigation