JA12 Battery Storage Requirements

JA12 is the Joint Appendix that sets the qualification requirements a battery energy storage system must meet before it counts toward Title 24 compliance. A new single-family home does not have to install a battery, but if it takes credit for one, the battery must be certified to the Energy Commission as meeting JA12. New homes with service over 125 amps must also be battery-ready.

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What JA12 is

Joint Appendix JA12 is part of the 2025 Reference Appendices. It sets the qualification requirements for a battery energy storage system (BESS) used to meet the Energy Code, whether paired with on-site or community solar or installed on its own. JA12 describes the battery’s primary job as daily cycling: shifting load, using more of the home’s own solar, and working with the grid.

JA12 does not decide whether a building needs a battery. The code sections do that. JA12 decides whether a particular battery counts.

Required, credited or ready

For a new single-family home these are three separate questions.

Is a battery required? No. Section 150.1(c)14 requires solar PV on a new home, but not storage. The PV rules are on is solar required on a new home.

Can a battery earn credit? Yes, in two ways. Under Exception 5 to §150.1(c)14, the PV size calculated from Equation 150.1-C may be reduced by 25 per cent if the home also installs a JA12-qualified battery with a cycling capacity of at least 7.5 kWh. On the performance path, the compliance software counts a qualifying battery in the energy budget, provided its usable capacity is at least 5 kWh per building.

Must the home be battery-ready? Yes, if its electrical service is over 125 amps. See below.

Nonresidential buildings are different. There, every building required to have PV must also have a JA12 battery sized by its own equations. That is a separate set of rules, covered on commercial solar PV and battery requirements. Multifamily buildings have their own provisions as well.

What a battery must meet

To qualify, the battery must be certified to the Energy Commission against JA12.3:

  • Safety: tested to UL 1973 and UL 9540, with the inverter tested to UL 1741, Supplement SA or Supplement SB
  • Prescriptive use: a round-trip efficiency of at least 80 per cent, AC to AC, and energy capacity retention of 70 per cent of nameplate after 4,000 cycles under warranty, or 70 per cent under a 10-year warranty
  • Performance use: usable capacity of at least 5 kWh per building, with the same retention warranty

Control strategies

A JA12 battery has to be programmed, not just installed. Every qualifying battery must be remotely programmable and able to switch between strategies. It charges first from on-site solar when production exceeds the home’s load, and discharges first to the home’s own load. Grid charging is allowed off-peak where the utility permits it, and at any time ahead of severe weather, a Public Safety Power Shutoff or a demand response event.

At inspection the battery must be commissioned to one of these strategies:

  • Basic control: charges only from surplus solar and discharges when solar falls below the load
  • Time-of-use control: discharges in the highest-priced hours, with at least three seasonal schedules
  • Advanced demand flexibility control: basic or time-of-use, plus demand response under §110.12(a) and changes on signals from the utility or an aggregator
  • Separate battery control: for a battery without on-site solar, such as a home served by community solar
  • an alternative strategy approved by the Executive Director

Single-family homes carry one more rule. If the backup reserve is raised so that the cycling capacity falls below the compliance cycling capacity on the certificate, the battery must reset itself after 72 hours. Reserve changes made by the utility, grid operator, aggregator or manufacturer for severe weather or a power shutoff are excluded.

Battery-ready requirements

Section 150.0(s) applies to new single-family homes of one or two dwelling units whose electrical service is greater than 125 amps, unless a battery is installed. The home must have:

  • either battery-ready interconnection equipment with at least 60 amps of backed-up capacity and four battery-supplied branch circuits, or a raceway of at least 1-inch trade size from the main service to a subpanel for the backed-up circuits
  • at least four branch circuits grouped at one panelboard, including the refrigerator, a lighting circuit near the primary exit and a bedroom receptacle
  • a main panelboard busbar rated at 225 amps or more
  • space for a transfer switch within 3 feet of the main panel, with raceways installed to it

It is the electrical counterpart to the roof space reserved under solar ready requirements.

How to check a battery is qualified

Manufacturers certify batteries through the Energy Commission’s Solar Equipment Lists program, which publishes the list of certified energy storage systems and the 2025 JA12 declaration statements for integrated and field-assembled systems. Check the exact model there before it goes on the compliance documents.

The building department then checks three things under JA12.4: that the installed model is certified as qualified, that it is commissioned with one of the listed control strategies, and that the strategy and compliance cycling capacity match what the Certificate of Compliance assumed. If any of the three differs, the credit does not hold.

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