Tesla Motors Inc. will announce a home battery and a “very large” utility-scale battery on April 30, according to an e-mail sent to investors and analysts.
Power storage is one of (if not THE) biggest obstacle to relying on natural power sources (solar, wind, tidal, etc). You can't just fire up another field of turbines when demand goes up if the wind isn't blowing. Efficient power storage should be an easy sell for Tesla owners in particular because the time of day in which they are most likely to charge their cars is the evening, aka peak demand. Having the ability to charge their home batteries during off-peak hours and then shunting that power into their cars whenever it's needed is certainly beneficial. Hopefully usage of these batteries will spread beyond Tesla's car owners to level out demand peaks.
Solar and Wind are complementary though, which partially solves the problem. If the sun isn't shining, you most likely have enough wind to power a turbine, if you don't have the wind to power the turbine, you most likely have enough sun to make panels worth having around. Improved storage efficiency will definitely make renewable energy more economically viable though, and that means (hopefully) less fossil fuel emissions.
Isn't that pretty much the goal long term? Give out patents so that tons of people make products with specs you can anticipate so that you can provide optimized batteries for them? Ubiquity tends to make millionaires. Not always of the most deserving people, but all that wealth has to accrue somewhere.