Sempra Energy's natural gas distribution utility Southern California Gas Co. (SoCalGas) faces an $8 million fine from California regulators for allegedly failing to follow protocols for timely billing of thousands of customers in 2015 and 2016.

Los Angeles-based SoCalGas, which serves nearly six million meters, was cited by the California Public Utilities Commission (CPUC) for failing to issue and prorate timely monthly bills, resulting in higher-than-normal billings, and extending the billing period for a significant number of customers.

A utility spokesperson said SoCalGas is reviewing the decision to determine if it would appeal.

The CPUC's assessed penalty was more than $8 million, with $4.7 million to be used to reimburse 47,000 customers with a one-time $100 credit for delayed bills during the winter of 2015-16. Another $3.36 million would be allocated to the state general fund.

The five-member regulatory commission determined that SoCalGas failed to issue more than 13.57 million bills between 2014 and 2016, and extended the billing period for about 140,000 customers in November and December 2015. CPUC also found that SoCalGas failed to prorate more than 153,000 of the extended 13.57 million bills in which proration was required. It also said the utility failed to issue timely monthly bills to about 47,000 customers in 2015-2016.

The utility will not be allowed to recover from ratepayers more than $542,00 in costs for incremental meter readers nor $150,000 for temporary workers because of the billing problems.

Commissioner Clifford Rechtschaffen said the regulatory action sends "a clear message that we expect utilities to comply with the billing provisions in their tariffs, and if they do not, we will take appropriate enforcement action."

SoCalGas said estimated bills have been essentially eliminated since it transitioned to advanced metering in which customers have access to real time data, said spokesperson Melissa Bailey. "We maintain that our billing practices during the period in question were consistent with our CPUC-approved tariffs.”

State regulators opened a formal investigation in the case two years ago in a proceeding to consider penalizing the utility for billing snafus.