Workers install photovoltaic modules on a roof in Germany (Stefan Thiesen/Wikimedia Commons)

Tesla developing battery system for houses to store solar power

18 February 2015 | By David Rogers 6 Comments

Tesla Motors, the US company known for electric vehicles, is developing a battery system for houses that can store solar-generated power for when the sun isn’t shining. 

The claim was made by Elon Musk (pictured), the firm’s chief executive, during a conference call with Wall Street analysts earlier this week.

The idea is that the battery system would work in tandem with photovoltaic panels in the roof of a home. The batteries would store surplus electricity produced when the sun is shining and make it available when it isn’t.

It would allow residents to make proper use of the panels and also protect the grid from sudden fluctuations of feed-in current, which can be difficult to balance.

Musk said Tesla had already produced a successful design for the batteries, and suggested that the first public demonstration could begin in the next month or so, with production starting up by the end of August.

A subsidiary market for the batteries could be homes that do not have access to utilities, and could replace the diesel generator as a source of power. They could also be used to provide emergency power for homes in the event of a black-out. 

Elon Musk, chief executive, Tesla Motors

The idea of using car batteries to power a home while the car is in the garage has been around for a number of years. In 2011, Nissan built a “Kan-kan-kyo” house at its global headquarters in Yokohama. This used the firm’s lithium-ion LEAF battery as source of back-up power, with the potential to power a Japanese home for two days.

More recently, it has been suggested that the hydrogen fuel cell in the Toyota Mirai could store as much as 150Kwh of electricity, which is enough to run a home for about a week. Toyota executives say they have not decided whether to offer the power-out capability on the 200 Mirais that will be sold in the US next year.

Tesla last year announced plans for a $5bn “Gigafactory” to produce the lithium batteries used in its cars. Musk may be hoping to benefit from the falling cost of photovoltaics, and the increasing popularity of solar panels among American homeowners and legislators. The SolarCity company, which installs panels, and which is owned by a cousin of Musk, now has 168,000 customers. 

Tesla’s quarterly report, which was the occasion for the conference call, revealed a loss of $108m for the last quarter of 2014, even though the firm built 11,627 vehicles. Musk said he expected Tesla to sell 55,000 of its model S and X vehicles in the coming year.