Battery Storage
in California
NEM 3.0 made battery storage a different kind of decision. Not always the right one. Here's what to think about before adding a battery — or before signing a proposal that includes one.
When a battery makes sense ↓Why batteries became the conversation
For most of California's solar history, batteries were optional. Under NEM 1.0 and NEM 2.0, the utility paid roughly retail rate for the electricity your panels exported. The grid was effectively a giant free battery — you "deposited" daytime production and "withdrew" the equivalent at night, with the utility doing the storage work. A solar system without a physical battery worked fine, financially.
That changed in April 2023. Under NEM 3.0 (officially the Net Billing Tariff), the utility no longer pays retail rate for exported electricity. Compensation is now based on avoided cost — what the utility would otherwise have paid to procure that electricity — which is a small fraction of what you pay to pull power back from the grid in the evening.
You self-consume some daytime production and export the rest at low avoided-cost rates — then buy it back in the evening at much higher retail rates. Still better than no solar, but the export portion now contributes much less to the case.
Daytime surplus charges the battery instead of being exported cheaply. In the evening you discharge it to avoid high retail rates — and can export during specific high-rate windows to capture the arbitrage.
Don't treat the inclusion of a battery as automatically meaning the proposal is sound. The battery makes the math work only if it's sized correctly, priced reasonably, and matched to your actual usage. It can also be oversold, oversized, or paired with a solar system bigger than you needed. Both extremes happen.
When adding battery storage makes sense
The cleanest signal a battery probably makes sense: you pay high retail rates, your usage is concentrated in expensive evening hours, and your roof can support enough solar to charge a battery substantially during the day. For most California homeowners in single-family homes with reasonable roof exposure, all three hold. The harder questions are how big and which brand.
Signals a battery probably makes sense
- You have, or plan to have, an EV. EVs concentrate large demand into specific windows; a battery sized for that can substantially cut charging cost and changes the optimal solar size too.
- You experience frequent outages. PSPS events and aging infrastructure make backup capability valuable in ways the financial math doesn't fully capture.
- You have time-flexible high loads — heat pumps, pool pumps, EV chargers. Shiftable loads multiply the benefit of storage.
- You'll own the system 10+ years. Batteries pay back over a longer horizon than panels; a 3–5 year hold usually doesn't recover the investment.
Signals it needs harder analysis
- You're a low-usage household. Small absolute consumption means small absolute dollar savings, even at a good percentage. Resilience may still justify it; pure economics may not.
- Your usage is heavily daytime. If you self-consume most of your production directly, there's less left to store — the marginal benefit shrinks.
- The proposed battery is oversized. Capacity beyond what you use in evening hours doesn't generate proportional savings. "Future-proofing" is sometimes right, sometimes an upsell.
- An unfamiliar brand your installer can't service. The battery industry is consolidating; limited California service infrastructure means warranty trouble five years out.
If you already have solar and want to add a battery
This is a meaningfully different decision than including a battery in a new install. The key consideration: if you're on NEM 1.0 or 2.0, you have grandfathered status under the more favorable rules. Adding a battery alone, properly configured, does not affect that status. Adding solar capacity along with it can.
California allows a one-time expansion of up to 1 kW or 10% of original system capacity (whichever is greater) without losing NEM grandfathering. Larger expansions — or improperly configured battery additions — can transition the entire system to NEM 3.0 rates, potentially costing significant savings over the remaining grandfathering period.
- Confirm your current NEM status (1.0, 2.0, or 3.0) from your interconnection agreement or monthly bill.
- If you're on NEM 2.0 and adding a battery only, it can typically be done without affecting status — but configuration matters.
- If adding solar capacity too, check whether your original capacity gives headroom under the 10% / 1 kW rule.
- Whatever the installer says, get the configuration confirmed in writing before installation begins.
What to look at when a battery is in a proposal
Battery proposals have their own details that deserve scrutiny separate from the solar portion.
Brand and model
"Tier 1 battery" is marketing, not a spec. The proposal should name the specific model so you can verify what's installed.
Usable vs nameplate capacity
Usable kWh is what matters for your home — it can be lower than the nameplate, or reserve capacity for backup-only mode. Ask for the usable number.
Itemized pricing
If solar and battery are bundled into one "system price," you can't tell if the battery is priced fairly. Ask for battery, integration, inverter, and labor separately.
Warranty terms
Most reasonable batteries carry 10-year warranties guaranteeing capacity retention. Read what's covered, what voids it, and whether the manufacturer or installer honors it.
Mode of operation
Self-consumption, backup, or grid-services export — the configuration affects both the return and the day-to-day experience. The proposal should specify and explain it.
Inverter interaction
Adding to existing solar? DC-coupled, AC-coupled, or hybrid-inverter replacement each have different costs and efficiency. Your installer should explain the choice.
California's SGIP rebate closed to most applicants on December 31, 2025. If you're told you qualify for an SGIP rebate in 2026, confirm it independently — the program has multiple tiers with different timelines, and what's available has changed substantially.
When an independent review is worth it
If a battery is part of a new solar proposal, the battery questions are part of the larger proposal review — equipment, sizing, pricing, warranty, contract structure. If you already have solar and are weighing a battery or an expansion, a focused written answer to your specific question usually fits better. And if an existing battery isn't performing, or you're chasing warranty status on equipment from an installer that's gone, that's a recovery situation.
All of these are advisory services launching soon — the questions above are what they're built to answer.