https://arstechnica.com/information-technology/2018/07/last-quarter-us-households-added-36-megawatt-hours-of-batteries-to-their-walls/

A new report from GTM Research and the Energy Storage Association (ESA) says that US homeowners added 36 megawatt-hours (MWh) worth of batteries to their residences in the first quarter of 2018. That's more than the previous three quarters combined.

The gains were driven by local and state policies that actually reduced the value of standalone solar installations, the report said. Where once a California or Hawaii homeowner might have received significant compensation from the local utility for producing rooftop electricity, now those programs are being limited, so homeowners are turning to batteries to capture excess energy made during the day. In California, utilities are adopting so-called Time of Use pricing, so investing in a battery can help homes continue to run when prices are highest. Consequently, "California and Hawaii together constitute 74 percent of residential deployments on the quarter," according to the ESA.