The Heart of a Tesla in Your HouseSolarCity, the biggest installer of solar energy systems in the U.S., and Tesla Motors, the electric car startup, are intimately linked via Elon Musk, the Chairman of the former and CEO of the latter (on top of that, SolarCity was founded by cousins of Musk, and he apparently was the one who had the idea for the company). So it should come as no surprise that they are collaborating and sharing technologies. The companies have complementary products to begin with (your Tesla electric car will be as clean as can be if you charge it up with electricity from SolarCity solar panels...), but the integration is now getting deeper; SolarCity will now sell and lease a "home energy storage system" that is based on battery technology provided by Tesla Motors.
It not only provides backup power in case of power failure and the ability to go entirely off-grid if you have a solar system that generates enough power for the needs of your house, but it can also reduce electricity bills in areas where Time-of-Use dynamic pricing is used:
Reduce Your Electric Bill
An additional benefit of energy storage is to reduce peak-usage charges on your utility bill. Some utilities offer Time-of-Use (TOU) rate plans in which the price of electricity varies based on the hour of the day. Rates are higher during the afternoon when electric demand is at its "peak" across all utility customers.
A storage system may help you save more money by drawing power from your battery instead of from the grid during higher rates peak hours. You can then recharge your battery during lower rate, off-peak hours.
SolarCity's battery systems are currently on offer in SolarCity's service territory nationwide and for lease in some California markets.
See also: SolarCity on the Verge of its IPO