Solar Electric Power Association (SEPA) has ranked the top 10 utilities in the United States that had the most solar electricity integrated into their energy mix as of the end of 2007. The rankings are based on information provided through a survey of utilities and independent research. The full report, including utility rankings, is available for download at

“Based on recent announcements and internal discussions with utilities, SEPA anticipates that utilities will quickly become the largest and one of the most important customers for the solar industry,” said Julia Hamm, SEPA's executive director. “Whether solar electric systems are developed by utilities, their customers or solar companies, the utilities' proactive engagement with emerging solar technologies is important to the solar industry as a whole. This market survey and resulting rankings provide a baseline against which increased utility activity can be measured in the future.”

For total solar electric capacity by megawatt, Southern California Edison (SCE; Rosemead, California, U.S.) takes top honors as the most solar integrated utility with the most overall solar capacity (MW) and solar capacity per customer (MW/customer). SCE's long-standing contracts with the SEGS concentrating solar thermal (CST) plants drive its large number of solar megawatts. However, with several recent large-scale CST announcements by several other utilities, SCE's top ranking may no longer hold once these new plants are constructed.

In addition to overall rankings, additional top 10 lists were released based on the amount of solar electricity interconnected to the utility in two different configurations: the customer side of the meter and the utility side of the meter.

On the customer side of the meter, Pacific Gas & Electric (PG&E; San Francisco, California) was No. 1 for both the largest amount of overall solar capacity and the highest MW/customer, but the latter category is in striking distance for several public power utilities. On the utility side of the meter, SCE is the highest ranked utility both for overall MW as well as MW/customer, which drove its No. 1 total ranking.

The list diversifies when delved down further into the data and utility types are differentiated. On the customer side of the meter for public power utilities, Los Angeles Department of Water & Power (Los Angeles, California) is the most solar integrated in overall capacity, while Kauai Island Utility Cooperative (Kauai, Hawaii, U.S.) has the highest capacity per customer.

California — with its long-standing policies for solar market development — represents the majority of the highest rankings, but utilities in Arizona, Colorado, Hawaii, Illinois, Nevada, New Jersey, New York, Texas, Washington and Wisconsin also make the top 10 in many categories. Solar markets are expanding rapidly beyond California and when standardized by the number of customers, interesting results will continue to emerge in the coming years.