For seven years, a handful of homebuilders offered solar as an optional item to buyers willing to pay extra to go green.

Now, California is on the verge of making solar standard on virtually every new home built in the Golden State.

The California Energy Commission is scheduled to vote Wednesday on new energy standards mandating most new homes have solar panels starting in 2020.

If approved as expected, solar installations on new homes will skyrocket.

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Just 15 percent to 20 percent of new single-family homes built include solar, according to Bob Raymer, technical director for the California Building Industry Association.

“California is about to take a quantum leap in energy standards,” Raymer said. “No other state in the nation mandates solar, and we are about to take that leap.”

Locally, the cities of San Francisco and Fremont have already leaped ahead of the curve. The Fremont City Council last May followed San Francisco’s lead by mandating that solar panel systems be included in all new single-family and multifamily homes. The minimum size of panel systems are dictated by the size of the homes.

In late 2016, Fremont — home of Tesla’s electric vehicle manufacturing plant — also required new residential and commercial developments to be “EV ready.” As a result, a new single-family home in most cases needs a large specialized outlet and a dedicated circuit in the garage so a resident can plug in an electric vehicle charger, said Rachel DiFranco, the city’s sustainability manager.

New commercial or multifamily developments meanwhile must install electric vehicle charging stations in at least 10 percent of parking spaces.

The proposed new statewide rules would deviate slightly from another much-heralded objective: Requiring all new homes be “net-zero,” meaning they would produce enough solar power to offset all electricity and natural gas consumed over the course of a year.

New thinking has made that goal obsolete, state officials say. True “zero-net-energy” homes still rely on the electric power grid at night, they explained, a time when more generating plants come online using fossil fuels to generate power.

“Zero net energy isn’t enough,” said Andrew McAllister, one of five state energy commissioners voting on the new homebuilding standards. “If we pursue (zero net energy) as a comprehensive policy, we’d be making investments that would be somewhat out of touch with our long-term goals.”

While environmentalists and homebuilders praised the new standards, the proposed rules have some detractors who still support net-zero goals.

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“We’re happy they’re making good progress,” said Kelly Knutsen, technology advancement director for the California Solar and Storage Association, a solar-industry group. “We wish they would go further. There’s always compromises.”

All-electric homes

In addition to widespread adoption of solar power, the new provisions include a push to increase battery storage and increase reliance on electricity over natural gas. Among the highlights:

The new solar mandate would apply to all houses, condos and apartment buildings up to three stories tall that obtain building permits after Jan. 1, 2020.

Exceptions or alternatives will be allowed when homes are shaded by trees or buildings or when the home’s roofs are too small to accommodate solar panels.

Solar arrays can be smaller because homes won’t have to achieve true net-zero status.

Builders installing batteries like the Tesla Powerwall would get “compliance credits,” allowing them to further reduce the size of the solar system.

Provisions will encourage more electric use or even all-electric homes to reduce natural gas consumption. State officials say improved technology is making electric water heaters increasingly cost-effective.

The mandate dates back to 2007 when the state energy commission adopted the goal of making homebuilding so efficient “newly constructed buildings can be net zero energy by 2020 for residences and by 2030 for commercial buildings.”

Builders would prefer the state move slower in imposing the solar mandate, but most nonetheless should be prepared by mid-2020, said the Building Industry Association’s Raymer.

Meritage Homes currently installs solar on about 10 percent of its homes, and about 1 percent of them are net zero, a company official said. A KB Home official said his firm has built more than 6,000 solar homes in the past seven years, mostly in California. That’s 12 percent of the 49,600 homes KB Home sold in that period.

The new energy standards add about $25,000 to $30,000 to the construction costs compared with homes built to the 2006 code, said C.R. Herro, Meritage’s vice president of environmental affairs. Solar accounts for about $14,000 to $16,000 of that cost, with increased insulation and more efficient windows, appliances, lighting and heating accounting for another $10,000 to $15,000.

But that $25,000 to $30,000 will result in $50,000 to $60,000 in the owner’s reduced operating costs over the 25-year life of the home’s solar system, Herro said.

Related Articles California homebuyers’ wish lists rarely include solar Bill Watt, a homebuilder and design consultant, said those added costs – on top of other building mandates like fire sprinklers – are pushing home prices further out of reach for many buyers.

Environmentalists, however, praised the new standards.

“The technology is developing so fast, we think the timeline was a bit slow,” said Kathryn Phillips, director of Sierra Club California.

Pierre Delforge, energy efficiency program director at the Natural Resources Defense Council, called the proposed update “another important step toward the environmentally-friendly, healthy and affordable home of the future.”