Assemblywoman Lori Saldana has introduced a bill that would require new homes built after 2020 to be net producers of energy

They may tap into solar power systems, wind turbines, or, perhaps, ground-source heating and cooling systems. Or they may use a combination of those technologies. But in some form or fashion, California Assemblywoman Lori Saldana says, new homes being built a decade or so from now should be zero-energy dwellings.

That is the focus of a bill the San Diego Democrate has introduced for consideration in the coming days by the California State Assembly Committee on Natural Resources. Saldana had proposed similar legislation last year that passed the Assembly but died in the state Senate.

The bill has the support of environmental groups such as Environment California, which envisions using the power grid like a battery that stores electricity generated by the homes’ alternative-energy sources during the day and feeds it back into the homes at night.

The bill’s requirements would go into effect on January 1, 2020, or when the California Energy Commission determines that use of solar systems is cost-effective, whichever comes later, a recent Associated Press story noted.

Part of bill’s viability is in fact pegged to the notion that mainstream adoption of solar energy systems will, with the help of state and federal rebates and tax incentives, increase over the next 10 years to the point where the cost of purchase and installation will be about half what it is now.

Opponents of the proposal point out that by focusing solely on new homes, the bill addresses a relatively small sector of energy consumers and contributors to greenhouse gas emissions. Tim Coyle, senior vice president of the California Building Industry Association, told the AP that new homes being built in California today already are highly energy efficient, and that older homes are far worthier candidates for efficiency upgrades.

“If the goal is to reduce fossil fuel dependency, why not go where the problem is?” Coyle said.