2 isle firms to offer Tesla home battery

Two of the largest solar companies in Hawaii are gearing up to offer off-grid solutions to customers, as Sunrun Inc. joined SolarCity in marketing a new home battery system.

San Francisco-based Sunrun and San Mateo, Calif.-based SolarCity account for roughly 50 percent of the solar installations in Hawaii. The two announced they will be offering Tesla Motors Inc.’s Powerwall home battery, the energy storage system Tesla launched Thursday night.

Powerwall, with a starting price of $3,500, can link to a rooftop solar system. The 51-inch-tall, 34-inch-wide and 7-inch-thick battery can supply most of the power to a home even on consecutive cloudy days, the companies said.

Instead of a rooftop solar system sending its excess power into the grid, that power would be used to charge the battery. Then at night or on a cloudy day, the home would draw power from the battery.

The batteries will first be sold as a backup to the grid, but by fall 2016 the companies will market the batteries as a way for a homeowner to disconnect from the grid.

Robert Harris, Sunrun’s Hawaii director of public policy, said the home battery system has the capability of taking half of Hawaii utility customers off-grid.

"It would be entirely possible to take half the load of Hawaii offline," Harris said. "It used to be speculative, people going off-grid and (using) batteries. Now it’s starting to become real. Fundamental to this is the fact that these batteries are relatively inexpensive."

Friday was the first day customers could order Powerwall.

Hawaii regulators have supported the use of batteries. The Public Utilities Commission ordered Hawaiian Electric Co. in March to come up with a plan to expand rooftop solar in the islands through better use of battery systems.

Hawaii’s solar industry has taken a hit in recent years after HECO began requiring in 2013 that homeowners get its approval before installing solar systems. The utility was slow to approve solar systems in areas that already had a high level of solar.

HECO is working with solar companies to integrate more energy storage, said Darren Pai, HECO spokes­man.

"Energy storage, both residential and utility-scale, can create great opportunities for our customers, improve reliability and support our state’s clean energy transformation," Pai said. "As part of the PUC process, we’re working with local and national PV companies to develop options for customers interested in this technology that will ensure safe, reliable service."