Battery storage transforms ADU solar economics in Belmont under PG&E's NEM 3.0 net billing rules. A Tesla Powerwall, Enphase IQ Battery, or FranklinWH paired with your ADU solar lets you store cheap solar energy and use it during expensive peak hours.
Title 24 does not require a battery on most ADUs in Belmont — only solar PV. Batteries are optional, but the math has shifted dramatically under NEM 3.0: exporting solar energy to PG&E now pays roughly 75% less than it did under the old NEM 2.0 program.
That means storing your ADU solar energy in a battery and using it later is now significantly more valuable than exporting it. Most Belmont homeowners adding solar to a new ADU are also adding at least one battery.
Most ADUs in Belmont pair well with a single 10–13.5 kWh battery — enough to run essential loads (refrigerator, lights, internet, mini-split HVAC, EV charging at low amperage) for 12–24 hours during a PG&E outage.
PG&E time-of-use rates create a large price spread between peak (typically 4–9 PM) and off-peak hours. A battery lets your ADU store free solar energy during the day and discharge it during peak — avoiding the highest-priced kWh charges entirely.
In Belmont (climate zone 3), a properly sized solar + battery ADU system typically achieves payback in 7–10 years under NEM 3.0, compared to 12–15+ years for solar alone.
Adding a single 13.5 kWh battery to your ADU solar project in Belmont typically adds $9,000–$13,000 cash. After the 30% federal Investment Tax Credit, the effective cost drops to $6,300–$9,100. SGIP rebates may further reduce cost for qualifying PG&E customers in San Mateo County.
A battery-equipped ADU keeps essential loads running during PG&E grid outages — including PSPS (Public Safety Power Shutoff) events that affect parts of California each fire season. For tenants in Belmont who work from home or rely on medical equipment, this is often the deciding factor.
No. California Title 24 requires solar PV but does not mandate battery storage on ADUs in Belmont. Batteries are optional but increasingly common under NEM 3.0.
Tesla Powerwall 3 is the most common choice for Belmont ADUs due to its integrated inverter and 13.5 kWh capacity. Enphase IQ Battery 5P is preferred for modular sizing on smaller systems.
Yes. The 30% federal Investment Tax Credit applies to standalone batteries 3 kWh or larger, even if installed without solar — though most Belmont ADU projects install both together.