NORTH COUNTY - The head of a consumer watchdog group Tuesday defended the group's support for a $120 million alternative to the $1.3 billion power line San Diego Gas & Electric Co. wants to build across the desert and mountain backcountry.

Responding to utility charges over the weekend that the group grossly underestimated costs, Michael Shames, executive director for the Utility Consumers' Action Network, stood by its $120 million estimate.

"Our proposal would achieve the same goals for one-tenth the cost," Shames said, in a meeting with the North County Times editorial board.

With the goals of boosting the reliability of San Diego County's power supply and bringing in power from nonfossil-fuel sources such as solar, wind and geothermal energy, the utility is proposing to build a 150-mile superhighway of electricity.

Dubbed the Sunrise Powerlink, the 500-kilovolt transmission line would run from El Centro to San Diego. Strung from towers as tall as 150 feet, its wires would wind through Anza-Borrego Desert State Park, Ranchita, Santa Ysabel, Ramona, Rancho Penasquitos and Carmel Valley.

The project is supported by many in the business community. It is sharply opposed by environmentalists and many residents of the communities the wires would cross, as well as local utility critics such as the Utility Consumers' Action Network.

In defense of the power line, San Diego Gas & Electric Co. filed 260 pages of reports with the California Public Utilities Commission late Friday, challenging reports filed earlier in the month by opponents.

In the latest filing, the company charged that the San Diego-based consumer group underestimated the cost of its alternate plan by more than $100 million.

As a result, the plan "crumbles under the microscope," Scott Crider, San Diego Gas & Electric Co.'s public affairs manager for the Sunrise Powerlink, said in an interview Friday.

The group's plan calls for upgrading the existing 230-kilovolt transmission line that runs along the coast instead of building a new power line. The coastal line connects San Diego Gas & Electric's territory in San Diego and southern Orange counties with Southern California Edison's territory to the north.

Crider said the group missed the point that its proposal would require upgrading the smaller wires that extend from the transmission line to deliver electricity to businesses and homes.

In the editorial board meeting, Shames disputed the company's assertion that the group made a mistake.

But even if it should turn out that San Diego Gas & Electric Co. is right and the cost is $100 million higher, the alternate plan still would be less expensive and deliver more bang for the buck than would the Sunrise Powerlink project, he said.

"Not only does this project not make sense environmentally, because it goes through a state park, it doesn't make sense economically," Shames said.

Utility officials say the power line would be designed to deliver 1,000 megawatts, boosting San Diego County's electricity supply by 20 percent.

The consumer group's proposal would boost the supply by 350 to 400 megawatts, Shames said.

A megawatt is the standard measuring unit for electricity. Typically, it is enough to keep the lights on in 1,000 homes, although much more is required on hot summer days.

The Public Utilities Commission filings, called testimony, will help frame a vigorous Sunrise Powerlink debate that is scheduled to take place in hearings throughout July in San Diego. The commission is scheduled to decide in January whether to grant permission to build the line.

After reviewing the most recent filings, San Diego County business leaders issued a news release Tuesday reiterating their support for Sunrise.

"Reliable power is the cornerstone of long-term economic prosperity," said Barbara Walden, chairwoman of the Community Alliance for the Sunrise Powerlink and president of the Downtown San Diego Partnership. "Delaying the Sunrise Powerlink is too big a risk for an economy so dependent on reliable power."

- Contact staff writer Dave Downey at (760) 740-5442 or ddowney@nctimes.com.