The report pegged the cost of adding storage to PV on the order of $700-1,300/kWh of storage capacity and the present-value benefit to the host customer of roughly $500-1,000/kWh.

Berkeley Lab’s Behind-the-Meter Solar+Storage: Market Data and Trends report said that through year-end 2020, roughly 550 MW of storage has been paired with solar in behind-the-meter (BTM) applications, mostly in the residential sector, and the “vast majority” in California.

The report said that roughly 6% of all U.S. residential PV systems installed in 2020 and 2% of non-residential PV systems included storage, though much higher rates have been realized within individual states and utility service territories.

Hawaii had “by far” the highest storage attachment rate of any state, the report said, at 80% residential and 40% non-residential. It credited the rate to net metering reforms that incentivize self consumption. California was second with attachment rates of 8% for residential and 2% for non-residential. Deployment there was largely driven by incentives and wildfire resilience issues.

In select pockets, attachment rates were 10-20%, including in areas served by Arizona’s Salt River Project and Washington State’s Puget Sound Energy.

Among paired residential systems installed in 2020, most used a single 5 kW battery with either 9.3 kWh (LG Chem RESU 10H) or 13.5 kWh (Tesla Powerwall) of storage capacity. The report said that the portion of systems installed with multiple batteries has been steadily growing (40% in 2020). Most residential systems have the ability to store 30-80% of average daily PV generation, depending on the relative size of the PV and storage components.

Read more: pv magazine