State regulators Monday proposed an aggressive statewide energy strategy that would push developers to build homes and shopping centers so efficient they would require no electricity or natural gas from California's major utilities.

While the proposal by California Public Utilities Commission officials would not require builders to meet deadlines, it would set a goal of building only so-called "zero net energy" homes by 2020 and only stores that require no outside energy by 2030.

The idea would be to design houses and commercial buildings to use little electricity and natural gas in the first place and to get whatever energy they use from on-site sources such as rooftop solar panels.

A building industry representative expressed doubts about whether it is a realistic goal, while a prominent consumer advocate suggested it is achievable.

In unveiling the proposed decision, Commissioner Dian M. Grueneich and administrative law Judge Kim Malcolm wrote: "This decision institutes a comprehensive, long-term energy efficiency strategy to achieve our ultimate goal -- making energy efficiency a way of life."

The Public Utilities Commission is scheduled to take up the proposal Oct. 18.

Paul Tryon, chief executive officer for the San Diego County Building Industry Association, said in a telephone interview that, while having 100 percent self-sufficient homes may be an admirable goal, it also may not be practical.

"It's a pretty assertive goal that will require an evolution in technology," Tryon said.

According to San Diego Gas & Electric Co., about 1.3 percent of the region's supply comes from rooftop panels, and the share is expected to reach 4 percent by 2015.

He said much progress has been made in the campaign to make buildings more efficient. New homes, for example, use 70 percent less energy than same-size houses built just 15 years ago, he said.

"California has led the country in being sort of friendly in its consumption of energy, with both new homes and new commercial buildings," Tryon said. "But this will require quite a stretch to get to the next level."

Scott Anders, director of the University of San Diego's Energy Policy Initiatives Center, said the goal is achievable, but significant obstacles will have to be overcome.

"The biggest challenge is air conditioning," Anders said, noting much of the state's growth is taking place in inland regions such as Riverside County and eastern San Diego County that swelter in summer.

"The goal is going to be difficult because most of the new houses are going to be built in the hotter climates," he said.

Still, Anders said, he lives in a nearly self-sufficient home in the inland community of Lakeside that he rebuilt following the 2003 Cedar fire.

"We did an energy-efficient design. It's nothing out of the ordinary, really," he said. "And then we have a (solar) photovoltaic system." So far, he said, the home is requiring zero electricity from the power grid.

The solar panels, however, were expensive, Anders said, adding that it remains to be seen whether the housing market in this costly region can support the expense of panels on every roof.

San Diego consumer advocate Michael Shames, executive director of Utility Consumers' Action Network, said by e-mail that he believes the proposed goal is "certainly" achievable.

"Most estimates suggest that solar will be considerably less expensive by 2020," Shames said. "With the advent of plug-in cars and lower photovoltaic prices, there's little reason why any new home shouldn't be a zero-net energy structure. Most customers will be able to produce most of the power they need, with the utility infrastructure serving more of a back-up function for new homes."

The commission's proposal would apply only to regions of the state served by California's major investor-owned utilities, such as San Diego Gas & Electric Co., which serves San Diego County and southern Orange County, and Southern California Edison, which serves Riverside County and the Los Angeles area.

Utility officials said they needed to study the proposal before commenting about its details.

"This is a little unusual," said Gil Alexander, a Southern California Edison spokesman.

Rachel Laing, a San Diego Gas & Electric spokeswoman, said: "It's in line with our general philosophy that energy efficiency is the first and most important pillar of our long-range planning."

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