Northwest Natural Gas Company will issue an Interstate Storage credit to its Oregon customers on their June bills for the 13th year in a row. 

This year's credit is for approximately $11 million and will equate to about $12 for the average residential customer in Oregon or nearly $48 for the average commercial customer. 

The credit is being given because of efficient pipeline capacity management and effective use of the company's underground natural gas storage facility in Mist, Oregon, during the 2013 calendar year. The technique used to make the most of these resources is called "optimization." 

In the last 13 years, savings provided back to customers from the company's Mist gas storage operations have totaled more than $96 million.