SAN DIEGO -- For the cost of constructing a controversial 150-mile power line through the backcountry, San Diego County could boost its electricity supply about the same amount by offering incentives to home and business owners to install solar panels on roofs, a new report says.

Utility officials and supporters of the proposed power line immediately criticized the report Thursday, calling it unrealistic. Environmental groups and elected officials who oppose the line commended the study as a forward-thinking, practical blueprint for steering society into a new era of clean electricity generation.

Authored by local engineer Bill Powers, a prominent power-line opponent, the report states that a $700 million incentive program could multiply the local energy supply from solar panels from just under 40 megawatts today to 920 megawatts in 2020. Powers said he was asked to tackle the project by the San Diego Foundation, which was seeking to examine alternatives to the Sunrise Powerlink.

With a 1,000-megawatt capacity, the proposed 500-kilovolt Sunrise transmission line that San Diego Gas & Electric Co. wants to build would run through Ramona, Rancho Penasquitos and Anza-Borrego Desert State Park. A megawatt, the standard measuring unit of electricity, is generally enough power to keep the lights on in 750 to 1,000 homes, although more is needed on hot summer days.

Christy Heiser, a San Diego Gas & Electric spokeswoman, said, "We encourage healthy debate about the future."

However, Heiser said, utility officials do not believe that Powers' blueprint will work.

"From the solar aspect, we don't believe it is a realistic plan," she said.

San Diego Councilwoman Donna Frye, speaking at a news conference in downtown San Diego to release the report, disagreed, calling Powers' plan is a realistic model for "local, secure and decentralized energy."

Also speaking at the outdoor conference was Assemblywoman Lori Saldana, D-San Diego. "Today's weather demonstrates why San Diego has the potential to lead the state in moving toward renewable energy," Saldana said, referring to the clear, sun-filled sky.

The rooftop solar strategy is the cornerstone of the report's suggested blueprint for meeting San Diego County's electricity needs between now and 2020, with the goal of slashing greenhouse gas emissions associated with the power supply by one-third. The blueprint also proposes to curb electricity use through conservation and better building design.

"Global warming is the issue of our time, and we must achieve the maximum feasible reductions in greenhouse gases," Powers said in introducing the report.

By following the blueprint, the region could triple the portion of its electricity that is generated today from solar and other nonfossil-fuel sources to 36 percent by 2020, the report states. And if regional leaders were to decide on a ratepayer-financed incentive budget twice as big -- $1.5 billion -- as much as half of San Diego County's electricity could come from such sources.

The 158-page report is titled, "San Diego Smart Energy 2020: The 21st Century Alternative." It was written by Powers, prepared by E-Tech International of Santa Fe, N.M., and funded by a $30,000 grant from the San Diego Foundation. The foundation is a charitable group that has awarded more than $400 million in grants for quality-of-life projects over three decades.

The report's conclusions were attacked by supporters of the Sunrise Powerlink, a $1.3 billion project that is projected to cost regional ratepayers $7 billion over 40 years. Because San Diego Gas & Electric customers would be asked to foot 10 percent of the cost, the report assumes that at a minimum, area consumers would pay $700 million. That's the money Powers proposes to shift to rooftops.

"I think Mr. Powers' plan is completely unrealistic," said Todd Voorhees, vice president of public policy and communications for the Downtown San Diego Partnership, and a spokesman for a coalition of county businesses that back the transmission line project.

Voorhees said the problem is that even with incentives, homeowners would wind up paying thousands of dollars up front to install solar panels.

"I definitely don't have the money to do that," he said. "And I don't think most other people do, either."

However, Powers said the plan assumes that only about 10 percent of the solar would be on homes. He said the rest would come from large solar photovoltaic systems -- ones capable of storing electricity -- on the broad roofs of big factories and office buildings.

"With the incentive budget, the cost of solar power will be at or below the utility rate that they are paying right now for their electricity," Powers said.

Maintaining that the plan is indeed practical, Powers said San Diego's public school system could serve as a model. The report states that the district contracted with a Los Angeles firm to install panels on 14 schools, with the ability to generate 5 megawatts. The firm owns the panels.

Besides the financial incentives, Powers said San Diego Gas & Electric could help by creating a rate structure that encourages people to install solar panels. And the state could help by opening a way for solar panel owners to sell their surplus power to the electric grid.

"The obstacles in the way are hundreds of years of utility policies," Powers said.

Henry Abarbanel, a Del Mar councilman and co-chairman of the San Diego Association of Governments' energy working group, said by telephone later that the report could play a key role in a planned five-year review of a regional energy strategy the association adopted in 2003. That strategy set a goal of securing 75 percent of the region's supply from sources within San Diego County by 2020, yet 67 percent of its power comes from outside the region today.

"It is an absolutely critical piece of information," Abarbanel said. "Everybody's overall goal is to have access to renewable energy, particularly solar. The question is, what's the most reliable way to do that?"

The energy working group has yet to take a position on the power line.

San Diego Councilwoman Donna Frye, who opposes Sunrise Powerlink, said at the news conference that she intends to ask a San Diego City Council resources committee to endorse the report.

Contact staff writer Dave Downey at (760) 745-6611, Ext. 2623, or ddowney@nctimes.com.