The primary function of the battery storage system is to grid harmonize the onsite PV system with the grid, to maximize benefits to the grid, environment, and the occupants.
Grid harmonization: For the purpose of Building Standards, “grid harmonization” is defined as strategies and measures that harmonize customer-owned distributed energy resources assets with the grid to maximize self-utilization of PV array output, and limit grid exports to periods beneficial to the grid and the ratepayer. Grid harmonization is done by charging the battery from the PV system when there is limited electrical load at the building and the cost of electricity is low in midday, and discharging when the cost of electricity is high, usually in the late afternoon and early evening hours.
The battery storage system is available as a compliance credit in the performance compliance method and is a prescriptive requirement for specific nonresidential and hotel/motel as specified in Section 140.10(b). In all cases, the battery storage system must meet all applicable requirements in Joint Appendix JA12 and be self-certified to CEC by the manufacturer as a qualified product.
Coupling a PV system with a battery storage system and appropriate control strategy, described in Section 9.5.2 below, allow reaching specific target time-dependent valuation (TDV) targets and source energy with a smaller PV system than otherwise would have been possible. This strategy is useful and cost-effective for meeting target TDVs that may be required by reach codes, with a smaller and grid-harmonized PV system.
The list of qualified JA12 products can be found at