California is the largest US solar market — and one of the most complex for compliance. Three investor-owned utilities, a post-2023 net metering overhaul, mandatory solar on new homes, and an advanced interconnection framework make California rules unlike any other state.
This guide covers the specific requirements that every California solar installer needs: NEM 3.0 economics, Title 24 mandates, Rule 21 interconnection, and how AHJ permitting works across the state’s major markets.
California Solar Market Scale
California installed more solar than any other US state in 2024, with over 85 GW cumulative capacity across utility, commercial, and residential segments. The state has over 1.5 million residential solar installations. Despite NEM 3.0’s impact on new residential economics, California remains the top US market for solar+storage systems.
NEM 3.0: The Current Net Metering Tariff
The CPUC adopted Net Energy Metering 3.0 (NEM 3.0) in December 2022. All new residential solar interconnections filed after April 14, 2023 are on NEM 3.0.
How NEM 3.0 Works
NEM 3.0 replaces flat retail-rate compensation with Avoided Cost Calculator (ACC)-based export rates. These rates:
- Vary by time-of-use (TOU) period and month
- Average approximately $0.05–0.08/kWh (compared to $0.28–0.35/kWh retail rates under NEM 2.0)
- Are higher in summer evenings (5–9 PM) when grid demand peaks
- Require a TOU rate plan
NEM 3.0 Export Rates by Time of Day (Approximate, 2026)
| Time Period | Approximate Export Rate |
|---|---|
| On-peak (4–9 PM, summer) | $0.10–0.16/kWh |
| Mid-peak | $0.04–0.08/kWh |
| Off-peak (overnight, morning) | $0.02–0.04/kWh |
| Super off-peak | $0.01–0.02/kWh |
NEM 3.0 Economics Require Battery Storage
The NEM 3.0 export rates make solar-only residential systems much harder to justify on payback alone. Payback periods for solar-only systems increased from 6–8 years under NEM 2.0 to 9–12 years under NEM 3.0. Solar+storage systems, however, retain strong economics: the battery stores midday solar production and discharges during the expensive evening peak hours, replacing grid import at retail rates of $0.28–0.35/kWh.
NEM 2.0 Grandfathering
Customers who applied for interconnection under NEM 2.0 before April 15, 2023 are grandfathered on NEM 2.0 terms for 20 years from their Permission to Operate (PTO) date. These systems retain retail-rate compensation and are exempt from NEM 3.0 rules.
Grandfathered NEM 2.0 customers can add battery storage without losing their NEM 2.0 status — the CPUC ruled that storage additions do not trigger NEM 3.0 reclassification.
Community Net Metering / VNEM
California allows Virtual Net Energy Metering (VNEM) for multi-tenant buildings. Under VNEM, solar production from a building-level system is allocated to individual meters within the building (apartments, commercial tenants) based on a pre-defined allocation percentage. This is distinct from the individual NEM 3.0 tariff for single-meter customers.
Title 24: Mandatory Solar on New Construction
California Title 24 Part 6 (California Energy Code) mandates solar PV on new buildings:
Residential Requirements (Single-Family)
Effective January 1, 2020:
- All new single-family homes must include solar PV
- Required system size formula:
kWdc = 1.00 × CFA/1000 × MAWhere CFA = conditioned floor area (ft²), MA = multiplier based on climate zone (0.572–1.375)
Residential Requirements (Multi-Family)
Effective January 1, 2023:
- All new multi-family buildings up to 3 stories must include solar PV
- Required capacity based on total conditioned floor area and building type
- Must meet Community Solar or on-site generation requirements
Commercial Requirements
New commercial buildings must meet the non-residential lighting power density and energy performance standards, which include renewable energy provisions. Large commercial buildings (>10,000 sq ft) have solar-ready requirements.
Title 24 vs. Customer Choice
Title 24 sets the minimum solar system size for new construction. Customers and builders can install larger systems. For the NEM 3.0 economics analysis on new construction, the Title 24-required system is typically the minimum — storage sizing is an additional decision based on load profile and TOU optimization.
Rule 21 Interconnection
Rule 21 is the interconnection tariff for PG&E, SCE, and SDG&E. It governs the technical and procedural requirements for connecting to the utility grid.
Rule 21 Application Process
| Step | Timeline | Notes |
|---|---|---|
| Submit interconnection application | Day 1 | Online via utility portal (Rule 21 application fee varies by system size) |
| Initial review | 10 business days | Utility confirms application completeness |
| Supplemental review (if triggered) | 30+ days | Required for larger systems or constrained circuits |
| Approval / Permission to Operate | Varies | Residential: 2–6 weeks typical; Commercial: 1–6 months |
Smart Inverter Requirements
California Rule 21 requires all grid-tied inverters to support advanced grid functions:
| Function | Requirement |
|---|---|
| Volt-VAr | Inverter adjusts reactive power output based on voltage |
| Volt-Watt | Inverter reduces real power output during high-voltage events |
| Frequency-Watt | Inverter provides frequency response |
| Default operating mode | Rule 21 default settings pre-programmed |
These functions are enabled by IEEE 1547-2018 compliant inverters and were required in California ahead of most other states. Most modern inverters sold in the US support these functions. Confirm with the manufacturer that the specific model supports California Rule 21 settings.
AHJ Permitting in California
California has thousands of AHJs — each city and county building department sets its own permit process. Key standardization efforts:
AB 970: Streamlined Residential Permits
California Assembly Bill 970 (effective January 1, 2015, strengthened in subsequent years) requires California AHJs to streamline permit review for residential solar systems:
- Systems up to 10 kW: Over-the-counter approval within 3 business days
- Pre-approved permit applications based on standard equipment lists
- Reduced or waived plan review fees for qualifying systems
SolarAPP+ in California
Many California cities and counties participate in SolarAPP+ for automated plan review:
- Systems under 15 kW on single-family homes
- Instant approval certificate after online submission
- Sacramento, Fresno, San Bernardino, and many others participate
- Check current participating jurisdiction list at solarapp.nrel.gov
Major California AHJ Notes
| City/County | Permit Portal | Notable Rules |
|---|---|---|
| Los Angeles | LADBS online portal | Solar permitting hotline available; AB 970 compliant |
| San Francisco | SF DBI | Historical buildings add complexity; SF has own solar guidelines |
| San Jose | SJ Permit Center | SolarAPP+ participant; online submission preferred |
| San Diego | City of SD DSD | SolarAPP+ participant; SDG&E territory |
| Sacramento | Sacramento City | SolarAPP+ participant; strong solar program |
| Unincorporated LA County | LA County DPW | Separate from City of LA; different process |
California Solar Contractor Licensing
| License | Scope | Issuing Authority |
|---|---|---|
| C-46 Solar Contractor | Solar PV system installation (not general electrical) | CSLB |
| C-10 Electrical Contractor | Electrical work including solar | CSLB |
| B General Building Contractor | Structural work; may subcontract electrical | CSLB |
The C-46 license is solar-specific and allows the full scope of residential solar installation without a separate electrical license. However, the C-46 does not allow general electrical work outside the solar scope — if panel upgrades or EV charger installation are part of the job, a C-10 is required.
License verification: california.gov/contractors (CSLB license lookup)
California SGIP: Self-Generation Incentive Program
The Self-Generation Incentive Program (SGIP) provides rebates for battery storage:
| Customer Type | 2026 SGIP Rebate Level (approximate) |
|---|---|
| Residential (general) | $0.20–0.25/Wh |
| Residential (equity/PSPS) | $0.85–1.00/Wh |
| Commercial | $0.15–0.20/Wh |
| Large commercial | $0.10–0.15/Wh |
SGIP rebates are available for storage systems installed with or without solar, but NEM 3.0 economics make solar+storage the dominant installation type. SGIP funds are allocated in budget steps — when a budget step sells out, the next step opens at a lower rebate level.
Design California Solar+Storage Projects with Accurate NEM 3.0 Economics
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Frequently Asked Questions
What is NEM 3.0 in California?
NEM 3.0 is the current net metering tariff for PG&E, SCE, and SDG&E customers, effective April 15, 2023. It replaced retail-rate NEM 2.0 compensation with Avoided Cost Calculator (ACC)-based export rates averaging $0.05–0.08/kWh — roughly 75% below the prior retail rate. NEM 3.0 favors solar+storage systems over solar-only.
Does California require solar panels on new homes?
Yes. Title 24 Part 6 has required solar PV on new single-family homes since January 1, 2020. The required system size is calculated using conditioned floor area and climate zone. Multi-family buildings up to 3 stories were added to the requirement in 2023.
What licenses are needed to install solar in California?
A C-10 (Electrical Contractor) or C-46 (Solar Contractor) license from the CSLB is required. The C-46 covers residential solar installation scope. A C-10 is required for additional electrical scope such as main panel upgrades.
