No — California Title 24 does not require battery storage on Accessory Dwelling Units. Solar PV is required on most new detached ADUs, but batteries remain optional. That said, adding a battery has become significantly more attractive under NEM 3.0 because exported solar is now worth ~75% less than self-consumed solar.
The 2022 Title 24 standards include a PV mandate for new low-rise residential, but the battery storage requirement only applies to multifamily and certain nonresidential buildings. Single-family homes and ADUs may use batteries to reduce required PV size, but are not forced to install one.
Under NEM 3.0, exported solar is credited at the avoided-cost rate (often 5–8¢/kWh) while imported electricity costs 35–55¢/kWh during peak hours. A battery captures excess midday solar and discharges it during the 4–9 PM peak window, raising effective savings by 40–60%.
Most ADUs use 5–10 kWh of batteries paired with a 2–4 kW PV system. Common choices include the Tesla Powerwall 3 (13.5 kWh), Enphase IQ Battery 5P (5 kWh modular), and FranklinWH (15 kWh).
Yes. Title 24 allows a 'PV+Battery compliance pathway' that reduces required PV kW when a qualifying battery is included.
For most ADUs we recommend the Enphase IQ Battery 5P (modular, AC-coupled) or Tesla Powerwall 3 (largest capacity, integrated solar inverter).
Yes. Standalone or solar-paired batteries qualify for the 30% federal Investment Tax Credit through 2032.