❓Can I Oversize a Battery Compared to Solar Under NEM or NBT in California?
Updated: June 24, 2025
Short answer: Yes—for now. But that could change after August 16, 2025.
⚖️ What Is the 150% Storage Sizing Limit in NEM/NBT?
California’s Net Energy Metering (NEM) and Net Billing Tariff (NBT) programs have long included a rule that limits battery size to no more than 150% of the paired solar system’s nameplate capacity (kW). The original goal was to prevent oversized battery installs using token solar to access NEM benefits like:
Grid upgrade cost exemptions
Avoiding departing load charges
⏸️ Is This Rule Being Enforced Right Now?
No. The 150% storage cap is on pause — and has been since 2020, when the CPUC suspended it to support wildfire resilience efforts.
The pause was extended in 2023 for two more years.
It currently applies to both NEM and NBT systems.
The rule technically still exists in the tariff but is not being enforced at the moment.
So yes — for now, you can oversize your battery relative to your solar system.
🗓️ What Happens After August 16, 2025?
The storage sizing cap is scheduled to return on August 16, 2025 unless the CPUC takes further action.
Any interconnection applications submitted on or after that date will be required to conform to the 150% rule.
Projects submitted before August 16 that are free of deficiencies (except the building permit) will not be affected.
🔄 Can the Rule Still Be Changed?
Yes — and action is already underway.
The California Solar & Storage Association (CALSSA) filed a petition last year to remove the cap permanently. The CPUC denied it, stating the utilities might propose a better path forward. But after no utility follow-through, CALSSA filed a new compromise petition in June 2025.
If approved, it would:
Eliminate the 150% limit, and
Add limited oversight for unusually large storage projects.
💡 What Should You Do?
If you're planning a solar + battery project with a large storage system, here’s what we recommend:
Submit your interconnection application before August 16, 2025
Ensure it is free of deficiencies other than the final building permit
Work with an experienced contractor who knows the rules
🛠️ Why Work with Us?
At Ally Electric & Solar, we’re one of the most experienced solar + storage contractors in the Bay Area when it comes to NEM, SGIP, interconnection rules, and battery sizing strategy. We help homeowners and businesses:
Navigate policy changes
Maximize rebates and incentives
Stay fully compliant while planning for resilience
📞 Have Questions? Let’s Talk.
If you're thinking about adding a battery or increasing your energy independence, we’re happy to walk you through your options. Now is the time to act—before the rules change again.