http://www.greentechmedia.com/articles/read/sizing-the-us-solar-plus-storage-market

Solar-plus-storage deployments totaled 4 megawatts (DC) in 2014, but GTM Research expects them to grow to 22 megawatts in 2015 and reach 769 megawatts by 2020. California is expected to be the biggest solar-plus-storage market, with 422 megawatts installed in 2020 alone. In dollar terms, we expect the market to grow to $246 million in 2015 and $643 million in 2016. By 2020, the annual U.S. solar-plus-storage market will be $3.1 billion.