Elon Musk, the billionaire entrepreneur who unveiled his “Powerwall” home battery Thursday, is already offering them to SolarCity Corp. customers seeking backup supply when the grid goes down.

The battery “replaces noisy, dirty fossil-fuel generators with zero-emission storage technology,” SolarCity said Thursday in a statement. Musk, whose Tesla Motors Inc. developed the product, is also chairman of the San Mateo, California-based solar supplier.

Musk is expanding beyond electric cars to sell batteries to homes and businesses seeking reliability as the grid absorbs more clean -- yet intermittent -- energy. Tesla’s battery can store power at peak production and dispense it later at less than half the cost of current systems, according to SolarCity.

“The mainstreaming of storage solutions may ultimately spur a transformation in how electricity is produced,” Pavel Molchanov, an analyst at Raymond James Financial Inc. in Houston, said Friday in a note to clients. “Tesla’s focus on behind-the-meter opportunities means that it’s getting into the newest, least established component of the storage space.”

“In contrast to the century-old model of centralized power plants and long-distance transmission lines, the rise of distributed generation” can in the “very long run lead to the obsolescence of the traditional utility model,” Molchanov said.

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‘Fusion Reactor’

Musk is seeking to solve this issue with a battery that costs more than 60 percent less than previous residential solar power storage systems, SolarCity said in the statement.

“We have this handy fusion reactor in the sky called the sun, you don’t have to do anything, it just works -- shows up every day and produces ridiculous amounts of power,” he said Thursday at Tesla’s product announcement.

“The obvious problem with solar power is that the sun does not shine at night,” Musk said. “The issue with existing batteries is that they suck, they’re really horrible.”

SolarCity is offering two payment options. For a 10 kilowatt-hour system, customers can prepay $5,000 for a nine-year lease, which includes installation, a maintenance agreement, the electrical inverter and control systems, Jonathan Bass, a spokesman, said in an e-mail Friday. Customers can also buy the same system outright for $7,140, Bass said.

Business

For businesses, SolarCity will incorporate the Tesla batteries into its DemandLogic storage system, which is used to dispense stored power when prices are high. It will also use the batteries in its GridLogic service that provides clean power to remote communities.

Tesla will also work with the energy software company EnerNOC Inc. to use the batteries to offset power use in commercial and industrial buildings during periods when grid power is in high demand, starting with select EnerNOC customers in California, the Boston-based company said Friday in a statement.

“Batteries, solar projects and other on-site energy systems -- that’s the muscle that’s being put in the system and EnerNOC’s software is the brains to make all that muscle work,” Tim Healy, EnerNOC’s chief executive officer, said in an interview Friday.

SolarCity began taking orders for the Tesla batteries Friday and expects to deliver them in October. The company had been installing power storage systems on a limited basis.

More Opportunity

Black & Veatch, an infrastructure builder, plans to work with Tesla on building power storage systems for commercial and industrial customers, the Overland Park, Kansas-based company said Friday in a statement.

SunPower Corp., the second-largest U.S. solar manufacturer, began offering power storage systems to customers in new homes built in California by KB Home last June.

“To the extent that Tesla does a great job, that’s good for that emerging segment and that’s good for SunPower,” CEO Tom Werner said in an interview. “I’m excited. The larger the market, the more opportunity there is.”

Sunrun Inc., a SolarCity competitor, also will sell Tesla’s home battery system, the company said Friday. The Vermont utility Green Mountain Power Corp. also plans to offer the Tesla battery system, it said in a statement.

Musk owns 21.4 percent of SolarCity and is the company’s largest shareholder as of Apr. 23, according to data compiled by Bloomberg. He owns 22.4 percent of Tesla, as of Dec. 31.

(An earlier version of this story corrected SolarCity Corp.’s name in the first paragraph.)