While batteries will supplement electricity derived from utilities via the power grid system, in the near-to-mid-term future, storage doesn't cause grid defection.
Manghani said it's unlikely that homes will be running entirely on solar power and batteries. To get off the grid with the same level of reliability as the grid, will require a huge battery, Manghani said.
However, there are benefits that energy storage can provide today, including back-up power during outages and a reduction in peak demand charges for commercial customers, which typically use the most electricity during the day.
Batteries will afford "time-of-use shifting," where businesses can purchase their power at low retail prices or store excess solar generation and consume it during peak hours.
"Not a lot of residential customers are on time-of-use tariffs, so this particular benefit is open only to a small portion of residential customers," he added.
Tesla got scooped
Tesla's news last evening was undercut by an announcement earlier in the day by German battery maker Sonnenbatterie and U.S. solar panel installer Sungevity. The two announced a partnership to offer battery storage systems to commercial and residential customers.
While pricing for Sonnenbatterie and Sungevity's integrated battery system has yet to be finalized, John Ordoña, Sungevity's vice president of communications, said prices will start below $10,000.
Sonnenbatterie's storage systems use Sony's Fortelion lithium-ion cells with up to 10,000 charge cycles.
"By installing the storage system, customers will be able to bank any excess energy generated by their solar panels and store it for future use, such as at night, during peak pricing hours or when there is a power outage," the companies stated in their announcement.
Sungevity customers in the U.S. and Europe will be offered Sonnenbatterie's smart energy storage systems in the second half of this year.
"The system is then combined with panels, solar inverters and other components into one Sungevity Energy System that's installed at the customer's home or business. The purchase will be as easy and straightforward as it is to purchase one of our solar systems today," Ordoña told Greentechgrid.com.
Musk, however, said Tesla's battery system technology and its operations for the Gigafactory will be open source, just as the company has done with its all-electric vehicle "Superchargers," which cut electric-vehicle charging time in half.
Musk referred to the Gigafactory as a product, not just a manufacturing facility, but together with other companies adopting the technology, fossil fuel use for electricity can someday be eliminated.
"We're not thinking of it in the traditional way people think of it as a factory ... what we're really designing in the Gigafactory is a giant machine," Musk said. "This is not something we think Tesla will do alone. There's going to need to be many other companies building Gigafactory-class operations of their own. We hope they do."
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