California Solar Production: NEM 3.0 Changed the Math, Not the Panels

California has more residential solar than any other state — well over a million homes, with installed capacity that dwarfs every other market. But April 15, 2023 quietly changed the entire economic equation for new installations: the California Public Utilities Commission's Net Billing Tariff (commonly called NEM 3.0) replaced the long-running Net Energy Metering 2.0 program, and the value of every kilowatt-hour you export to the grid dropped substantially.

The panels still produce the same kilowatt-hours they always did. The math underneath those kilowatt-hours is what changed — and that means how you should think about underperformance has changed too.

NEM 2.0 vs. NEM 3.0: The Compensation Cliff

For most of California's solar boom, residential systems were compensated under NEM 2.0. Under NEM 2.0, every kilowatt-hour you exported to the grid was credited at approximately the full retail electricity rate — the same price you'd pay to buy that kilowatt-hour back at night. That created a simple, generous economic model: oversize your system, "bank" credits during the day, draw them down at night and through the winter.

NEM 3.0 (formally the Net Billing Tariff) ended that. Under NEM 3.0, exports are compensated at "Avoided Cost Calculator" values — wholesale-plus rates that depend on time of day, season, and grid conditions. In simple terms: instead of getting credited at retail (often $0.30+/kWh in PG&E, SCE, or SDG&E territory), exports are typically credited at rates that are a small fraction of that, with some peak-hour windows worth meaningfully more.

The CPUC's stated goal was to shift the economic incentive toward consumption-matching solar paired with batteries: solar that serves your own load when it's producing, and batteries that store excess for use during peak evening hours when grid value is highest. For homeowners, the practical consequences are real: a NEM 3.0 system without storage produces the same kWh as a NEM 2.0 system but generates much less bill savings.

NEM 3.0 / Net Billing Tariff was approved by the CPUC in December 2022 and took effect for new interconnection applications submitted on or after April 15, 2023. Existing NEM 2.0 customers are generally grandfathered.

If You're on NEM 2.0: Grandfathering and What It Protects

If your system was interconnected under NEM 2.0 (interconnection application before April 15, 2023), you are grandfathered into NEM 2.0 compensation for a defined period — commonly cited as 20 years from your original Permission to Operate (PTO) date. That grandfathering is a meaningful financial asset.

But grandfathering only protects the compensation structure. It does not protect against:

• Panel degradation. Crystalline silicon panels lose roughly 0.5%/year of capacity. After 10 years, your system produces about 5% less than it did at commissioning, even if it's running perfectly. That's expected. What's not expected is the 15-25% shortfalls we see in systems with module-level faults, inverter degradation, or inverter clipping that nobody flagged.
• Equipment failures. A single failed microinverter, a tripped string, or a degraded module can shave several percent off production. The owner often doesn't notice for months because the bill still looks "okay" — just not as good as last year.
• Installer disappearance. Your NEM 2.0 grandfathering survives your installer going under. Your monitoring portal might not. Your production guarantee (if you have one) becomes harder to enforce.
• Lost grandfathering risk. Major system modifications — substantially increasing capacity, replacing the inverter with a higher-capacity unit — can in some cases trigger a re-evaluation under NEM 3.0. The rules are nuanced; if you're considering an upgrade, confirm with your utility before signing.

For NEM 2.0 grandfathered customers, every kilowatt-hour of underperformance still translates roughly to retail-rate dollars lost. The math is the same as it always was. The cost of inattention is high.

If You're on NEM 3.0: Why Production Tracking Matters More, Not Less

There's a common misconception that NEM 3.0 makes solar "not worth monitoring" because exports are worth less. The opposite is true. Under NEM 3.0, every kilowatt-hour you self-consume is worth full retail value — because you're avoiding a kilowatt-hour you'd otherwise buy. Only exports earn the lower wholesale-style rate. So:

• Self-consumption is your highest-value kWh. A working solar system displaces grid imports during the day, which are valued at full retail rate ($0.30+/kWh in many cases). Underperformance during your home's load hours hits you at retail-equivalent rates.
• Time-of-day production matters. Late-afternoon and early-evening exports (under the right peak windows) earn more than midday exports under the Avoided Cost Calculator. Inverter clipping, panel soiling, or shade that disproportionately affects peak-hour production has outsized financial impact.
• Battery dispatch depends on accurate production data. If your inverter is reporting wrong production numbers, your battery may be charging at suboptimal times. Independent verification matters when the system's own monitoring is what's making the dispatch decision.

The Installer Bankruptcy Wave: SunPower, Sungage, and the Aftermath

California's installer market has been turbulent. SunPower — long the premium-positioned national installer — filed for Chapter 11 bankruptcy in August 2024. Sungage Financial, a major solar loan provider for many California installers, also faced significant restructuring. Smaller regional installers have closed at higher rates than usual since 2023, partly driven by the NEM 3.0 transition reducing new-customer demand.

If your installer is gone or unstable, several things change:

• Workmanship warranties may be unenforceable. Equipment warranties (panels, inverters) generally pass through to the manufacturer, but the labor warranty — the part that pays a technician to come fix the issue — depends on the installer being around to honor it.
• Production guarantees become difficult to enforce. If your contract included a production guarantee, who do you submit a shortfall claim to when the company is in bankruptcy?
• Monitoring portals may go dark or be migrated. SunPower's monitoring has been transitioning to new ownership; customers have reported gaps and confusion during the transition. If you rely on an installer-branded portal to know whether your system is working, that's a single point of failure when the installer disappears.

For more on what to do if your installer is no longer operating, see our guide on solar installer bankruptcy.

What to Track If You're a California Solar Owner

Whether you're grandfathered on NEM 2.0 or new to NEM 3.0, the underlying question is the same: is your system producing the kilowatt-hours it physically should, given your location, orientation, and the weather that actually happened?

1. Actual vs. weather-adjusted expected production. Year-over-year comparisons mislead in California because solar irradiance varies meaningfully with smoke from wildfires, marine layer changes, and rainfall patterns. The right baseline is a physics-based model of what your specific system should have produced given the actual weather, not a generic annual estimate.
2. Module-level performance (if you have microinverters or DC optimizers). A single failed microinverter on a 24-panel system is a ~4% production hit. Easy to miss in aggregate; obvious in panel-level data.
3. Inverter clipping during peak hours. Over-sized array on an under-sized inverter wastes the highest-value production. If clipping is severe, it's worth knowing.
4. Production guarantee status (if applicable). If your contract includes a guarantee, you have a deadline-bound claim window. Underperformance discovered after the reconciliation deadline is harder — sometimes impossible — to recover.

How OwlWatt Helps California Solar Owners

California's combination of high retail rates, the NEM 3.0 transition, and installer instability makes independent monitoring more valuable here than in most states. OwlWatt provides:

• Physics-based performance verification using NREL-validated irradiance modeling calibrated to your specific California location and system specifications
• Production guarantee tracking against your contract terms, with alerts well before reconciliation deadlines
• Dollar-denominated underperformance alerts tuned to your actual retail rate — whether you're on a PG&E E-TOU plan, an SCE TOU-D-PRIME plan, or SDG&E DR-SES
• Independence from your installer's monitoring portal — works regardless of whether your installer is still in business or your portal has migrated