NBT (Net Billing Tariff)

Key Takeaways

• NBT = California’s Net Billing Tariff (NEM 3.0).
• Solar exports at avoided-cost rates ($0.05–0.08/kWh average).
• Imports at retail TOU rates.
• Storage critical for restoring residential paybacks.
• See NEM 3.0 for full design implications.

How the Avoided-Cost Rate Is Set

NBT exports are priced against the CPUC’s Avoided Cost Calculator (ACC) rather than a flat feed-in rate, so the value of a kWh exported at noon can differ sharply from a kWh exported at 6 PM. Imports, by contrast, are billed at ordinary retail time-of-use rates — the asymmetry between a low avoided-cost export rate and a full retail import rate is what drives the payback math under NBT. Interconnection itself is governed separately under Rule 21, which is the technical tariff a system must satisfy before it can begin exporting under NBT at all.

Why Storage Changes the Calculation

Because exports are worth the least exactly when most residential systems produce the most (midday), shifting that same energy into the evening peak with a BESS captures a materially higher avoided-cost rate instead of exporting it cheaply. This is why NBT-era system designs increasingly pair PV with storage sized for self-consumption and time-shift rather than maximum export, and why payback period estimates for solar-only systems have lengthened compared to legacy net metering.

Related Reading

Homeowners and EPCs evaluating whether a project pencils out under NBT should start from realistic system sizing rather than a legacy net-metering assumption — sizing guidance for common residential system sizes is a useful reference point before layering in storage economics. On the permitting side, projects in California still need to clear local plan review under the state’s own code stack, and the California AHJ solar permit guide covers the Title 24 and NEC requirements that run alongside — but separately from — NBT billing rules.