The short answer
- You can add a battery to most existing solar systems with an AC-coupled battery that has its own inverter.
- The installer needs a C-10 (Electrical) license; a C-46 solar contractor may install a battery only along with new solar (CSLB).
- It needs a permit and a new interconnection application with your utility.
- On NEM 2.0, ask for written confirmation that your tariff and anniversary date won't change (keeping NEM 2.0).
Is it worth it on NEM 2.0?
On NEM 2.0, exports already earn close to retail credit, so a battery mainly adds backup power and some savings from shifting use into the 4–9 p.m. peak. On net billing, a battery is what makes solar pay: it saves midday solar for the evening, when power costs the most.
What the job involves
- A site visit: main panel capacity, where the battery can go (garage, outside wall), and which circuits to back up.
- A permit from your city; batteries over certain sizes or in certain spots need fire review (permits and fire code).
- An interconnection application with your utility for the battery.
- Install, inspection and permission to operate.
Watch for
- A main panel upgrade, if the panel can't take another backfed breaker (the 120% rule).
- Whether the battery may charge from the grid; charging only from solar keeps NEM rules simple.
- Warranties on the existing solar if a different company touches it.
In the City of LA, LADBS issued battery-only permits as a separate category; see the City of LA page.
Checked against official sources on Oct 1, 2026. Sources are linked in the text. Not legal, tax or financial advice.