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SEPA 2013 Utility Solar Rankings Uncovers New Urban and Rural Representation

The Solar Electric Power Association (SEPA) has released its seventh annual Utility Solar Rankings report, a summary of U.S. utilities that added the greatest amount of solar capacity in 2013. As in years past, familiar names cropped up at the top of the list. But there were also a number of newcomers who made the grade — including two from previously unrepresented states — that reflect a growing diversity of geographies spanning urban and rural areas alike.

Rounding Up the Winners

Pacific Gas & Electric (PG&E) once again snatched up first place in total installed solar capacity, with 1,471 MW — a figure that dwarfed the competition and was more than double the amount of capacity installed by first runner-up San Diego Gas & Electric, which racked up 643 MW. This is the sixth year in a row that PG&E has topped the list of utilities for annual integrated capacity. Arizona Public Service came in third place, showing 417 MW. 

Scarcely a replay of past ranking reports, four utilities led by Duke Energy Progress made it into the top 10 for the first time. These four also include National Grid, Public Service Electric & Gas, and Georgia Power. 2013 is also the first year that utilities in Massachusetts and Georgia appeared on the list.

In the category of top 10 solar watts-per-customer, Massachusetts-based Sterling Municipal Light Department took top honors with 831 W. The watts-per-customer rankings calculate the number of customers served in relation to a utility’s installed solar capacity. This effectively levels the playing field and enables an across-the-board comparison between utilities, both large and small. PG&E came in sixth place in watts-per-customer, while San Diego Gas & Electric ranked second and Arizona Public Service came in fourth.

In a listing of the top 10 utilities with the greatest number of interconnections in 2013, PG&E once again took the number one spot with 28,807 projects ahead of Southern California Edison, which had 26,372. Hawaiian Electric Company placed third with 14,071 projects, but took first place when annual interconnections were compared on a per-thousand-customers basis. Kaua’i Island Utility Cooperative, Hawaii Electric Light Company, and Maui Electric Company Ltd. took second, third, and fourth places in the per-thousand rankings.

Key Report Findings

Analysis shows that 10 utilities accounted for 82 percent of all integrated solar capacity in 2013, a fact SEPA VP of Research and Strategy Eran Mahrer says is the result of large scale investments coming to fruition. “2013 was the year utility-scale solar took the lead in the type of capacity being deployed,” Mahrer said. “Large scale installations dominated the landscape and represented well over 50 percent of the capacity installed in 2013. This effectively pushed PG&E, SDG&E and Arizona Public Service to the top of the list.” Mahrer added that the increase in percentage dominance among the top 10 utilities — which grew from 73 percent in 2012 — is not indicative of those beyond the top 10 slowing down, but is instead a sign that top ranking utilities are building more on a large scale. 

Additional report findings show that 4.2 GW of solar capacity was installed in the U.S. in 2013, bringing total cumulative capacity to more than 10.5 GW. It was also reported that 70 percent of surveyed utilities presently offer their customers solar incentives, with 45 percent offering programs for key accounts.

AC versus DC

The data collected by SEPA was reported in alternating current (AC) units instead of direct current (DC), a point that Mahrer stressed is critical to gauging results accurately. “AC capacity is what’s ultimately used by the customer in the electric system,” Mahrer said. “The DC number is really of zero consequence.”

Miriam Makhyoun, Research Manager at SEPA, said this year’s report “took a more nuanced approach to applying derate factors” than it had previously. Instead of applying an 80 percent DC to AC derate, studies on residential and nonresidential systems were performed to arrive at a more accurate accounting of the real world electricity generation capacity of U.S. solar installations.

Top 10 Utilities by MW

  1. Pacific Gas & Electric (CA) 1471 MW
  2. San Diego Gas & Electric (CA) 643 MW
  3. Arizona Public Service  (AZ) 417 MW
  4. Southern California Edison (CA) 373 MW
  5. Duke Energy Progress (NC, SC) 137 MW
  6. National Grid (MA, RI) 111 MW
  7. Public Service Electric & Gas (NJ) 103 MW
  8. Hawaiian Electric (HI) 98 MW
  9. Georgia Power (GA) 59 MW
  10. Duke Energy Carolinas (NC, SC) 58 MW

Top 10 Utilities by Watts-Per-Customer

  1. Sterling Municipal Light (MA) 831 W
  2. San Diego Gas & Electric (CA) 461 W
  3. Silicon Valley Power/City of Santa Clara (CA) 427 W
  4. Arizona Public Service (AZ) 368 W
  5. Hawaiian Electric Company (HI) 329 W
  6. Pacific Gas & Electric (CA) 281 W
  7. Hawaii Electric Light Co. (HI) 182 W
  8. Maui Electric Company Ltd. (HI) 178 W
  9. Kaua’i Island Utility Cooperative (HI) 167 W
  10. Imperial Irrigation District (CA) 159 W

SEPA plans to release an Executive Summary on May 15 and a Utility Trends report on June 5 to provide more in-depth and qualitative analyses of their report findings.


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Italy’s well-known sun and sand form the basis of many beach holidays. An Italian company has also found another purpose for the combination: energy production.

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Vince Font is a freelance journalist specializing in the fields of renewable energy, high tech, travel, and entertainment. Read his blog at or follow him on Twitter @vincefont.


Volume 18, Issue 3


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