LOS ANGELES - California last week became the first U.S. state to require solar installations on most new homes by the year 2020.

The mandate on single-family houses and multifamily units of up to three stories is part of an effort by the state to cut carbon emissions. The mandate comes as Washington adopts less ambitious environmental goals to reduce what President Donald Trump calls job-killing regulations.

Supporters believe California's action will jump-start the growing U.S. solar power industry, while opponents view the move as unneeded interference in the marketplace. They say it places a burden on low-income residents.

Forty percent of solar installations in the United States are now in California, where public utilities are promoting solar panels and other forms of clean energy. 

“Over a quarter-million of our customers, residents and businesses already have solar installed at their property,” said Jill Anderson, vice president of customer programs and services at Southern California Edison, a utility power company that serves 15 million people. “We’re increasing that number by 4,000 to 5,000 new connections a month,” she said.

With the upcoming mandate, solar power will become nearly universal in the company’s service area.

Clean energy costs

Clean energy sources are getting cheaper, said professor Daniel Kammen of the Energy and Resources Group at the University of California, Berkeley.

“We are finding wind and solar in particular are frequently the least-cost options -- not just equal, but the least-cost options,” he said. “Arizona just did a bid, a tender,” Kammen noted, “and solar came in at under 2 cents per kilowatt hour. The next closest competitor was dirty, air-polluting coal at over twice that price.”

Critics complain that the solar mandate will raise construction costs by nearly $10,000 for the average home. For homeowners, the investment is worthwhile, said one solar power expert.

“They can save a little bit in the short term in construction,” said Peter Saeta, a physics professor at Harvey Mudd College in Claremont, California, “but it’s penny-wise and pound-foolish, certainly from a societal point of view,” given the high costs resulting from fossil fuel pollution.

Saeta said emission-free solar power lets homeowners recoup their investment through lower energy costs. According to state officials, solar power users can expect $19,000 in savings over a 30-year period.

Some critics don’t want government mandates, while others claim California’s housing is already too expensive and that the mandate will only boost an industry that is doing well on its own.

State officials said it’s an important part of their plan to reduce carbon emissions by 40 percent from 1990 levels by 2030.

Setting a goal

Kammen, of the University of California, Berkeley, said California can reach the goal, as can cloudier places like the city of Seattle in Washington.

“We find that by adding wind, and solar, and some storage around the big demand centers in Seattle and Richmond and some other places, that they could also reach goals like California’s, which are essentially to be entirely powered by clean energy,” Kammen said.

“And that story,” he added, “is replicated around the country,” using hydroelectric and geothermal, or other clean sources of energy.

A clean energy grid “starts with adding more renewable and carbon-free resources” to the supply, said Anderson, of Southern California Edison. A smarter electrical system, better-insulated buildings and improved solar-cell efficiency could get homes off the energy grid for days at a time.

“That’s coming,” Saeta said, based on “improvements in (solar) panels, improvements in the control electronics, improvements in smart devices that talk to each other, and battery technology.”

He is testing a modification in solar panels that could increase their efficiency by reducing the heat produced in solar cells.

Kammen said the federal government should raise the minimum standards for energy production to monitor, incentivize and “essentially bring up the floor. So, as some states like New York and Washington and Florida and California set very aggressive standards," he said, "a really wonderful job for the federal government” is to find “the least-cost, most-effective ways to bring these policies to Kentucky, Mississippi -- a variety of states that might not have been clean-energy leaders in the past.”

With or without federal action, supporters of the California mandate said the boost to the state’s economy, which is larger than those of France, India or Italy, may well spark an expansion of solar power around the United States.