NEM 3.0

Quick Facts

What is NEM 3.0?

Formal definition

NEM 3.0 is the popular name for California’s Net Billing Tariff (NBT), formally adopted by CPUC Decision 22-12-056 (December 15, 2022) and effective April 15, 2023. NBT replaces NEM 2.0 for new applications to PG&E, SCE, and SDG&E.

Engineering definition

Under NBT, solar exports are credited at hourly time-differentiated avoided-cost rates published in CPUC’s Avoided Cost Calculator. Imports are billed at retail rates (typically TOU). The system encourages solar customers to self-consume or time-shift exports via storage.

Industry definition

EPCs, installers, and design firms refer to “NEM 3.0” or “NBT” interchangeably. The policy reshaped California residential solar — battery attach rates jumped from 15% (pre-NBT) to over 60% (post-NBT).

Permitting definition

Not a permitting requirement per se, but utility interconnection applications now require the customer to acknowledge NBT terms and may impose specific inverter or metering requirements.

NEM 3.0 Explained Simply

For homeowners: Under the old rules (NEM 2.0), every kWh you sent back to the grid earned you the same price you paid to buy. Under NEM 3.0, exports earn much less — about 75% less on average. To make solar pencil out, you usually need a battery to use your own power at night instead of exporting it cheaply.

For installers: Solar-only proposals are harder to sell. Sell value with batteries. Run the customer’s TOU rate against the avoided-cost calculator to show the storage payback.

For designers: Optimize for self-consumption. Battery sizing now drives system architecture more than peak DC kW.

For new engineers: The hourly avoided-cost matrix is the new design input. Match generation profile + storage dispatch profile to the high-priced evening hours.

Analogy: NEM 2.0 was like selling apples at the same price the grocery store charges. NEM 3.0 is selling apples at the wholesale price. The smart move is to refrigerate apples (battery) and eat them yourself when prices are high.

Why NEM 3.0 Matters

Economic. Solar-only paybacks moved from 5–7 years to 9–14 years. Adding storage restores 7–10 year paybacks. The economic case for solar is intact but more nuanced.

Engineering. Battery sizing is now the central design decision. ILR (inverter loading ratio) trends down because clipped midday energy can’t be exported profitably.

Market shift. Battery attach rates jumped from 15% (2022) to over 60% (2024). Solar+storage is now the default residential offer.

Utility planning. NEM 3.0 reduces midday duck-curve over-supply. CPUC projects $2–4 billion in avoided cross-subsidy by 2030.

Permitting impact. UL 1741-SB inverters with grid-forming capability needed for NBT-aligned export schedules.

How NEM 3.0 Works

1. Energy import from the grid is billed at the customer’s TOU rate (typically $0.30–0.55/kWh in California).
2. Energy export to the grid is credited at the hourly Avoided Cost Calculator (ACC) rate for the customer’s weather zone.
3. Monthly billing nets the credit against import charges plus fixed charges.
4. Excess credits at year-end roll over (small projects) or are paid at avoided-cost rates (medium/large).
5. Storage operation can shift solar from midday low-value hours to evening high-value self-consumption.

Engineering Deep Dive

Avoided Cost Calculator (ACC) structure

ACC publishes 8,760 hourly export prices per weather zone × forecasted 25 years. For 2024:

• Spring midday (oversupply): $0.02–0.04/kWh
• Summer 4–9 PM: $0.20–0.80/kWh (peak)
• “Extreme heat” hours: up to $2.00/kWh
• Winter morning: $0.05–0.12/kWh
• Annual weighted average export rate: $0.05–0.08/kWh

Solar-only economics under NEM 3.0

A 6 kW system in Northern California:

• Annual production: 9,400 kWh.
• Self-consumption fraction (no storage): 35–45%.
• Exported energy: ~5,500 kWh @ avg $0.06/kWh = $330/yr export revenue.
• Self-consumed offset: 4,000 kWh × $0.35 TOU avg = $1,400/yr.
• Total annual savings: ~$1,730 (vs. ~$3,200 under NEM 2.0).
• Payback on $18,000 net cost: ~10–11 years.

Solar + storage economics

Same 6 kW + 13.5 kWh battery (Powerwall 3 or equivalent):

• Self-consumption fraction: 75–85%.
• Storage discharge during peak TOU = additional ~$0.45/kWh value over avoided-cost.
• Total annual savings: ~$2,500–2,800.
• Payback on $30,000 (with SGIP rebate): ~8–9 years.

Design implications

• Battery size to peak evening usage, not full daily.
• Inverter: UL 1741-SB hybrid (single device) often outperforms separate solar inverter + battery inverter.
• ILR: Drop from 1.25–1.35 to 1.15–1.20 because clipped solar can’t be exported profitably.
• Module orientation: West-facing modules now hold higher value than south because they generate in higher-priced afternoon hours.

Design Considerations

• Run ACC-based simulations in Aurora, OpenSolar, Energy Toolbase, or SAM. Don’t use generic kWh × retail-rate models.
• Customer TOU schedule. Combine ACC export with customer’s import TOU to optimize battery dispatch.
• Battery technology. LFP (lithium iron phosphate) dominates for cycle life under daily NBT-aligned dispatch.
• Inverter topology. AC-coupled vs. DC-coupled — DC-coupled is more efficient for new builds; AC-coupled simpler for retrofits.
• Backup vs. economic dispatch. Most NEM 3.0 customers want both; ensure the controller supports both modes.
• SGIP eligibility. Storage projects under SGIP have specific reporting and metering requirements.

Permitting Implications

• Inverter must be UL 1741-SB to handle NBT-aligned export schedules.
• Smart inverter functions enabled (Rule 21 phase 3) to manage exports.
• Production metering and export metering may both be required; check the utility’s interconnection rules.
• CSI Thermal / SGIP application for storage rebate (separate from interconnection).
• Title 24 still applies for new construction including solar-ready and battery-ready provisions.

Utility Interconnection Impact

NEM 3.0 sits on top of Rule 21 (the interconnection standard). Interconnection process steps:

1. Submit utility interconnection application (online portal).
2. Acknowledge NBT election (replaces NEM 2.0 election).
3. Receive Permission to Operate (PTO) after AHJ approval.
4. Utility installs production-export bidirectional meter (some service areas).

US Code Requirements

NEM 3.0 doesn’t change NEC 690 or 705 directly, but it interacts with:

• UL 1741-SB — Smart inverter capability required.
• IEEE 1547-2018 — Grid-support functions enabled.
• Rule 21 — California-specific interconnection.
• CALGreen / Title 24 — New construction solar mandates.

India Regulatory Context

Not directly applicable. India’s net-metering structure varies by state — Karnataka uses gross metering for large systems, Maharashtra uses net metering with banking limits, Gujarat mixes both. NEM 3.0 design lessons (storage-first design) increasingly inform Indian rooftop solar planning, especially as state ToD tariffs spread.

Software Applications

Aurora Solar (Design Mode)

Integrates ACC tables for accurate NBT economics. Generates customer-facing financial reports that compare NEM 2.0 vs. NEM 3.0 with and without storage.

Energy Toolbase

Industry-leading software for commercial NBT analysis. Models battery dispatch optimization against the customer’s specific TOU rate plus ACC export.

OpenSolar

Open-source residential design tool with NBT integration.

SAM (System Advisor Model)

NREL tool with full ACC-based modeling for utility-scale and commercial.

Real-World Examples

Residential — 8 kW + 13.5 kWh battery, San Jose

TOU rate (PG&E E-ELEC): $0.62/kWh peak (4–9 PM), $0.39/kWh part-peak, $0.36/kWh off-peak.

• Solar-only annual savings: ~$2,100.
• Solar + battery annual savings: ~$3,000.
• Customer added storage at $14,000 net (after SGIP rebate); payback ~5 years on the storage delta.

Commercial — 250 kW + 400 kWh storage, San Diego (SDG&E)

Demand charge offset dominates economics. Combined solar + storage cuts $48,000/year off the $135,000 baseline bill; payback 6.2 years on the storage-only delta.

Multi-family — 500 kW community solar

NBT-eligible community solar via SOMAH program. Storage layered to capture peak hours during summer Flex Alerts.

Common Mistakes

1. Using retail-rate net metering math. Always use ACC hourly tables.
2. Sizing battery to full daily load. Size to peak-hour offset (4–9 PM) for best ROI.
3. Forgetting SGIP rebate in financial models.
4. West-facing modules without east-facing balance. Mixed orientation often optimal.
5. DC-coupled storage on existing system without inverter swap. Verify retrofit feasibility.
6. Not modeling the customer’s specific TOU rate. PG&E vs SCE vs SDG&E have very different rate structures.
7. Assuming export rates will increase. ACC projections show some hours dropping below $0.02/kWh by 2030.
8. Treating storage as backup only. Economic dispatch dominates ROI in NEM 3.0.

Best Practices

• Run side-by-side NEM 2.0 vs. NEM 3.0 modeling for every customer proposal.
• Default to solar + storage for new residential projects.
• Use ACC tables in your design software; refresh annually.
• Educate customers on TOU schedule choice — wrong schedule kills the economics.
• Combine SGIP and Federal ITC for maximum incentive stacking.

Comparison Tables

NEM 2.0 vs. NEM 3.0 — Side by Side

Standards & Certifications

• CPUC Decision 22-12-056 — NBT adoption.
• Rule 21 (California utility tariff) — Interconnection standard.
• UL 1741-SB / UL 1741 CRD — Smart inverter listing for NBT export compliance.
• IEEE 1547-2018 — DER interconnection.
• IEEE 2030.5 — SunSpec common smart inverter protocol (utility communication).
• CSI Thermal / SGIP rebate programs.

Key Takeaways

• NEM 3.0 (NBT) replaced California’s net metering on April 15, 2023, slashing export rates from retail to avoided-cost.
• Solar-only payback stretched from 5–7 to 9–14 years; solar+storage paybacks 7–10 years are now the dominant offer.
• The Avoided Cost Calculator provides hourly export rates by weather zone — design and finance models must use these directly.
• Existing NEM 2.0 customers retain their tariff for 20 years from PTO date.
• UL 1741-SB smart inverters, SGIP storage rebates, and time-shift battery dispatch are the three design pillars of NEM 3.0-era California solar.