Gas Interchangeability Protocol Update Available

Friday, July 13, 2007

In response to a growing trend in the use of more non-traditional gas supplies such as liquefied natural gas, Pacific Gas and Electric Company has performed internal and external research to develop a gas interchangeability protocol and further identify gas quality limits for its system. PG&E has historically managed its gas system on a day to day basis using heating value as a primary interchangeability parameter. Research has shown however, that the Wobbe Index is a more effective predictor of gas appliance performance, and is therefore more suitable for use as a primary interchangeability parameter.

The research concluded that PG&E, subject to CPUC approval, should be able to accept gas that has a Wobbe index number of 1385 with a maximum heating value of 1100 Btu/scf. PG&E will conduct further appliance testing in August 2007 to determine a minimum Wobbe index number for its system. As additional findings are reached during PG&E's ongoing research, updates will be posted.

Gas quality interchangeability research is not limited to PG&E. Interstate pipelines interconnecting with PG&E are exploring possible changes to gas quality provisions. These changes may impact deliveries into the PG&E system in the future. If you have any concerns about interstate pipeline deliveries to California, please contact the pipelines directly. If you have questions regarding the Interchangeability Protocol Update, please contact Kimberly Kemp, by phone at 925.974.4266 or by e-mail