UL 1741 SA (Supplement A to UL 1741) is the product safety certification that demonstrates an inverter meets California's Rule 21 smart inverter requirements. SA stands for 'Smart Inverter Advanced Features.' An inverter with UL 1741 SA certification has been tested to confirm it supports Volt-VAr, Volt-Watt, Frequency-Watt, and other advanced grid functions required by the California Public Utilities Commission (CPUC).

UL 1741 SB (Supplement B) is the certification that demonstrates an inverter meets IEEE 1547-2018 requirements — the national standard for interconnecting distributed energy resources to US utility grids. SB requires advanced voltage and frequency ride-through capabilities, communications support, and the same grid support functions as SA (Volt-VAr, Volt-Watt) with nationally standardized default settings.

Which states require UL 1741 SA vs. UL 1741 SB?

California requires UL 1741 SA for all new grid-tied inverters. All other US states that have adopted IEEE 1547-2018 require UL 1741 SB. As of 2026, most states have formally adopted IEEE 1547-2018, making UL 1741 SB effectively the national baseline. Hawaii has its own requirements (Rule 14H) that overlap with but are not identical to SA or SB.

Can I use a UL 1741 SB inverter in California?

Yes, if it also has UL 1741 SA certification (dual-listed). Most major inverter brands carry both SA and SB listings on their current models. A UL 1741 SB-only inverter (without SA) may not satisfy California's Rule 21 requirements — the SA certification is the specific California requirement. Check with the utility or inverter manufacturer before submitting a California Rule 21 application with an SB-only inverter.

Does every inverter need UL 1741 SA/SB certification?

Every grid-tied inverter in the US must have UL 1741 certification (the base listing). The SA and SB supplements add advanced grid function requirements on top. For California installations, UL 1741 SA is required. For all other states that have adopted IEEE 1547-2018, UL 1741 SB is required. Inverters listed only under the base UL 1741 standard (without SA or SB) may not be acceptable for new installations in most states.

UL 1741 SA vs. UL 1741 SB: Inverter Certification Guide for Solar Installers

Every grid-tied solar inverter sold in the US must be UL 1741 certified — but in recent years, UL added two supplements (SA and SB) that are now required for most new installations. Understanding the difference matters for equipment selection, utility interconnection applications, and permit documentation.

Base UL 1741: The Starting Point

The base UL 1741 certification (Standard for Inverters, Converters, Controllers and Interconnection System Equipment for Use With Distributed Energy Resources) has been the foundational US inverter safety listing since the early 2000s. It covers:

Electrical safety (insulation, overcurrent, ground fault)
Anti-islanding (inverter disconnects when grid power is lost)
Basic voltage and frequency operating ranges

Most older inverters installed before 2018 carry only the base UL 1741 listing. These inverters were acceptable for interconnection at the time — but are no longer acceptable for new installations in most states.

UL 1741 SA: The California Standard

UL 1741 Supplement A adds the advanced grid functions required by California Rule 21. An inverter with SA listing has been tested to verify:

Function	SA Requirement
Volt-VAr	Must support; California-specific default curve
Volt-Watt	Must support; California-specific default curve
Frequency-Watt	Must support; California default settings
Soft start / ramp rate	Must support configurable ramp rates
Voltage/frequency ride-through	California-specific ride-through curves
Communications	Optional for small systems

The SA test report is California-specific — it uses California’s grid voltage and frequency parameters and default settings.

States requiring UL 1741 SA: California only.

UL 1741 SB: The National Standard

UL 1741 Supplement B certifies compliance with IEEE 1547-2018 — the national standard adopted by most US states starting around 2020–2022.

IEEE 1547-2018 vs. Rule 21 key differences:

Feature	UL 1741 SA (Rule 21)	UL 1741 SB (IEEE 1547-2018)
Voltage ride-through	California curves	IEEE 1547-2018 Category A/B curves
Frequency ride-through	California settings	IEEE 1547-2018 settings
Volt-VAr default	California curve	Nationally standardized
Communications	Optional	Required for 500 kW+
Reactive power capability	Required	Required

SB certification is recognized in all US states that have adopted IEEE 1547-2018 — which is now most states. A UL 1741 SB inverter can be used for utility interconnection in Texas, Florida, New York, Colorado, New Jersey, Massachusetts, Arizona, and all other non-California states.

Which States Require What

State	Required Certification
California	UL 1741 SA (+ SB accepted if also SA)
Hawaii	Hawaii Rule 14H (separate requirements)
All other US states	UL 1741 SB (for IEEE 1547-2018 adopted states)

Hawaii Is Different

Hawaii has its own advanced inverter requirements under Hawaiian Electric Rule 14H, which preceded both Rule 21 and IEEE 1547-2018. Hawaii requirements include additional functions not covered by either SA or SB. Inverters for Hawaiian Electric (HECO) and Maui Electric (MECO) installations should be specifically verified against Rule 14H requirements — most major brands have Hawaii-specific firmware or settings profiles.

Most Modern Inverters Are Dual-Listed (SA + SB)

For installers, the practical answer is: use any major-brand inverter from 2020 or later and it almost certainly has both UL 1741 SA and SB certification. The dual-listing means:

The same inverter can be used in California and any other state
No need to stock different inverter models for California vs. non-California projects
One set of firmware handles both SA and SB function sets

Inverter manufacturers include: Enphase, SolarEdge, SMA, Fronius, Hoymiles, Sungrow, Huawei (FusionSolar), ABB/FIMER, Solaredge, Generac PWRcell, and others.

How to Verify Certification Before Ordering

Method 1: Manufacturer’s product page

Go to the inverter manufacturer’s website → product certifications page
Look for “UL 1741 SA,” “UL 1741 SB,” or both
Many manufacturers list the UL certificate number

Method 2: UL Product iQ database

Search at productiq.ulprospector.com
Enter the inverter model number
Filter by “UL 1741” to see all certifications

Method 3: Ask the distributor

Solar distributors (CED Greentech, Renvu, BayWa r.e., etc.) maintain verified certification lists
Ask for a copy of the UL certificate for the specific inverter model

Documentation for Utility Interconnection

Most utility interconnection applications (California Rule 21, and other state interconnection processes) require documentation that the inverter is UL 1741 SA/SB certified. Include in the interconnection package:

Inverter datasheet with certifications listed
Copy of UL certificate (optional but recommended for large systems)
Statement in cover letter noting “All inverters are [Brand/Model], UL 1741 SA and SB certified”

Specify Code-Compliant Inverters for Every State

SurgePV’s equipment library flags UL 1741 SA and SB certification status for every inverter, ensuring you specify the right equipment for California and non-California projects.

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Frequently Asked Questions

What is the difference between UL 1741 SA and SB?

SA certifies California Rule 21 smart inverter compliance with California-specific grid settings. SB certifies IEEE 1547-2018 compliance with nationally standardized settings. Most modern inverters carry both. California requires SA; all other states require SB.

Which states require UL 1741 SA?

Only California. All other US states require UL 1741 SB (for states that have adopted IEEE 1547-2018). Hawaii has separate Rule 14H requirements distinct from both SA and SB.

Can I use the same inverter in California and other states?

Yes, if the inverter is dual-listed UL 1741 SA + SB (which most 2020+ major-brand inverters are). The same hardware supports both California’s Rule 21 settings and the national IEEE 1547-2018 settings through firmware configuration.