Net Metering and Its Impact on California Electrical Systems

Net metering is a billing and interconnection mechanism that directly shapes how distributed generation systems — primarily solar photovoltaic arrays — interface with California's investor-owned utility grid. The California Public Utilities Commission (CPUC) governs net metering policy for the state's three major investor-owned utilities, and the rules determine both the electrical design requirements for qualifying systems and the economic structure of grid export credits. For electrical contractors, system designers, and property owners, understanding net metering's technical and regulatory dimensions is inseparable from understanding California electrical systems broadly.

Definition and scope

Net metering, as defined under California Public Utilities Code §2827 and the CPUC's associated decisions, is a tariff arrangement allowing customers with eligible generating facilities to deliver surplus electricity to the grid and receive a compensatory credit against consumption charges. The mechanism applies to systems generating electricity from solar, wind, biogas, and fuel cell sources, though residential solar photovoltaic installations account for the dominant share of enrolled capacity.

California has operated under successive net metering frameworks. The original Net Energy Metering (NEM 1.0) program, followed by NEM 2.0 effective April 2016 (CPUC Decision D.16-01-044), imposed a one-time interconnection fee and non-bypassable charges on exported energy. The third iteration, NEM 3.0 — formally the Net Billing Tariff (NBT) — took effect for new applicants on April 15, 2023, per CPUC Decision D.23-02-015. Under NEM 3.0, export compensation rates are based on Avoided Cost Calculator (ACC) values rather than retail rates, a structural shift that reduces average export compensation by approximately 75 percent compared to NEM 2.0 (CPUC NEM 3.0 Fact Sheet).

Scope limitations: This page covers net metering as it applies to California's three investor-owned utilities — Pacific Gas & Electric (PG&E), Southern California Edison (SCE), and San Diego Gas & Electric (SDG&E) — under CPUC jurisdiction. Municipal utilities such as the Los Angeles Department of Water and Power (LADWP) or Sacramento Municipal Utility District (SMUD) operate independent net metering programs under different rate structures and are not governed by CPUC decisions. Federal interconnection standards under FERC jurisdiction establish a ceiling but do not displace California's state-level tariff rules. Matters outside CPUC authority, including municipal utility rate design, are not covered here.

How it works

Net metering operates through a bidirectional revenue-grade meter installed at the point of interconnection between a customer's generating system and the utility distribution network. The meter records both imported grid power and exported surplus generation. Under NEM 2.0, exported kilowatt-hours earned credits at the full retail rate, carried forward and applied against future consumption within a 12-month true-up period.

Under NEM 3.0's Net Billing Tariff, the compensation structure changes materially:

  1. Export compensation rate: Determined monthly using the CPUC's Avoided Cost Calculator, reflecting the marginal cost to the grid of displacing additional generation at each hour. Rates vary by time of day and season.
  2. Import charges: Customers continue paying applicable retail time-of-use (TOU) rates for all grid-imported energy.
  3. True-up cycle: Billing continues on a monthly basis with annual reconciliation, though the asymmetry between export compensation and retail import rates creates a stronger economic incentive for on-site consumption or paired battery storage.
  4. Interconnection application: Customers file a Generating Facility Interconnection Request (GFIR) through the relevant utility's online portal before installation. PG&E, SCE, and SDG&E each maintain distinct portals aligned with utility interconnection requirements.
  5. Permission to Operate (PTO): The utility issues PTO only after the Authority Having Jurisdiction (AHJ) has issued a final electrical inspection approval. Electrical work must comply with the California Electrical Code (Title 24, Part 3), NEC Article 690 for PV systems, and applicable utility technical requirements.

Common scenarios

Residential solar-only (NEM 2.0 grandfathered): Systems approved before April 15, 2023 retain NEM 2.0 terms for 20 years from their PTO date. These installations involve standard 120/240V single-phase service with a dedicated AC disconnect, anti-islanding inverter certification (UL 1741), and interconnection through the existing meter base or a new meter socket approved by the utility.

Residential solar-plus-storage (NEM 3.0): The reduced export compensation under NBT makes battery storage economically central. California energy storage electrical systems paired with solar require additional design elements: a battery management system, dedicated overcurrent protection, and compliance with NFPA 855 (Standard for the Installation of Stationary Energy Storage Systems) as adopted in California's Fire Code. Panel capacity is a limiting factor; many installations require a panel upgrade to accommodate combined loads.

Commercial and industrial systems: Systems above 1 MW are subject to the CPUC's Wholesale Distribution Tariff (WDT) rather than standard net metering. Systems between 10 kW and 1 MW follow NEM tariff terms but must satisfy additional study requirements through the utility's Distribution Planning process. California commercial electrical systems above certain thresholds may also trigger demand charge implications under time-of-use rate structures.

Virtual Net Metering (VNEM): Available for multifamily properties, VNEM allows a single generating system to allocate export credits across multiple separately metered tenant accounts. This structure is governed by CPUC Decision D.15-01-051 and intersects directly with California multifamily electrical requirements, particularly subpanel sizing and metering separation requirements.

Decision boundaries

The transition from NEM 2.0 to NEM 3.0 creates a set of classification boundaries that affect system design, permitting timelines, and economic modeling:

NEM 2.0 vs. NEM 3.0 eligibility: A system qualifies for NEM 2.0 grandfathering only if the interconnection application was submitted and deemed complete by the utility before April 15, 2023. Application date, not installation date, controls tariff assignment.

System sizing limits: California's standard net metering tariff applies to systems sized to meet, but not exceed, 100 percent of the customer's prior 12 months of consumption. Systems designed to exceed this threshold require CPUC approval or fall outside the standard NEM tariff framework entirely.

Aggregated net metering: Meter aggregation allows multiple meters on contiguous or adjacent parcels under common ownership to share credits from a single generating system. Not all utilities implement aggregation identically; applicants must verify eligibility under each utility's specific tariff schedule.

Permitting and inspection pathway: Every net metering installation requires a building and electrical permit from the AHJ — typically the city or county building department. The California electrical inspection process for solar interconnections includes a rough-in inspection (if applicable), a final electrical inspection, and utility meter verification before PTO. Some jurisdictions have adopted SolarAPP+ for automated permit issuance on straightforward residential systems, reducing approval timelines from weeks to under 24 hours in participating cities.

Safety classification: Anti-islanding protection is a non-negotiable safety requirement under IEEE 1547-2018, adopted by CPUC as the baseline interconnection standard. Failure of anti-islanding protection creates an electrocution hazard for utility line workers during grid outages. UL 1741 SA certification (Supplement A) is required for advanced inverter functionality mandated under Rule 21, the CPUC's interconnection tariff governing distributed energy resources.

For the full regulatory framing that governs these interconnection rules and their enforcement hierarchy, the regulatory context for California electrical systems provides the applicable code and agency structure.

References

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