Growatt WIT 40K-A-US L2

Name: Growatt WIT 40K-A-US L2
Brand: Growatt

Battery inverter, ac-coupled battery inverter. 4 models, 28 kW–55 kW AC at 208 V.

UL 1741 SBCEC listed · Jun 21, 2024

Model

Rated AC power40 kW
CEC weighted efficiency96.5%

Models & power ratings

CEC Grid Support Inverter List (Oct 7, 2026) · NLR SAM inverter library · 4 models

Model	Nominal AC	Grid voltage	CEC continuous	Rated AC (SAM)	CEC weighted eff.	DC test window	CEC listed	UL 1741 SB
WIT 28K-A-US L2	28 kW	208 V	27.9 kW	27.9 kW	97.0%	380–650 V	Jun 21, 2024	SB
WIT 35K-A-US L2	35 kW	208 V	34.9 kW	34.9 kW	97.0%	380–650 V	Jun 21, 2024	SB
WIT 40K-A-US L2	40 kW	208 V	39.8 kW	39.8 kW	96.5%	380–650 V	Jun 21, 2024	SB
WIT 55K-A-US L2	55 kW	208 V	54.8 kW	54.8 kW	96.5%	380–650 V	Jun 21, 2024	SB

Efficiency

CEC Grid Support Inverter List (Oct 7, 2026) · NLR SAM inverter library

CEC weighted efficiency96.5%
Night-time standby (tare)19.72 W
Power to start converting85.9 W

CEC weighted efficiency is measured by an accredited lab at six power levels and three DC voltages — the number to compare between inverters.

Grid & smart-inverter certification

CEC Grid Support Inverter List (Oct 7, 2026)

UL 1741 SB (3rd ed.)Yes — Intertek, certificate Nov 27, 2023
UL 1741 SA (SA8–SA13)Yes — Intertek
Firmware tested (SA)TO1.0
Volt-VAr with reactive power priority (SA13)Yes
Freq-Watt / Volt-Watt (SA14–15)Yes
Disable permit service / limit active power (SA17–18)Yes
CSIP (IEEE 2030.5) conformanceVia gateway during testing (Y*)
Monitor key data & scheduling (Rule 21 Phase 3)Yes (attested Jun 21, 2024)
Power control system (PCS)Stated in CEC listing (power control system)
CEC listedJun 21, 2024

UL 1741 SB is required for new interconnections in California (Rule 21) since 2026.

Compare with similar 40 kW inverters

CEC Grid Support Inverter List (Oct 7, 2026) · building permits

Inverter	Power	CEC weighted eff.	DC test window	UL 1741 SB	Latest CEC	SoCal permits
Growatt WIT xxK-A-US L2	28 kW–55 kW	96.5%	380–650 V	Yes	2024	0
Trystar OZPCS-RS35-FB0	24 kW–35 kW	95.0%	400–800 V	Yes	2025	—
Trystar OZPCS-RSxx-FB1	24 kW–40 kW	97.0%	400–820 V	Yes	2025	—
Trystar OZPCS-EP40-000	40 kW–40 kW	97.0%	550–820 V	Yes	2024	—
Trystar OZPCS-RS40-BB1	40 kW–40 kW	97.0%	550–820 V	Yes	2024	—

Same type and grid voltage, power range covering this model; same fields from the same sources.

About Growatt

CEC Grid Support Inverter List (Oct 7, 2026)

ManufacturerGrowatt
Listed in CEC asShenzhen Growatt New Energy Co., Ltd.
Websitegrowatt.com
Models on CEC lists539

Other series

WIT xxK-A-USWIT xxK-AU-USWIT xxK-AU-US L2

Questions & answers

How efficient is the Growatt WIT xxK-A-US L2?

The California Energy Commission lists a weighted efficiency of 96.5–97.0% for Growatt WIT xxK-A-US L2 models, measured at six power levels and three DC voltages.

What sizes does the Growatt WIT xxK-A-US L2 come in?

The CEC list includes 4 models from 28 kW to 55 kW AC: WIT 28K-A-US L2, WIT 35K-A-US L2, WIT 40K-A-US L2, WIT 55K-A-US L2.

Is the Growatt WIT xxK-A-US L2 certified to UL 1741 SB?

Yes — the CEC Grid Support Inverter List shows UL 1741 SB for all models.

Can the Growatt WIT xxK-A-US L2 be used with a battery?

The CEC lists it as a ac-coupled battery inverter.

What is the WIT 40K-A-US L2’s DC input voltage range?

CEC tested it at 380–650 V DC.

Sources

California Energy Commission — Grid Support Inverter List (solar and battery inverters), data as of Oct 7, 2026. Manufacturer-reported, confirmed by CEC against certificates and test reports.
NLR (formerly NREL) — System Advisor Model CEC inverter library (version 2026.7.3).
Building permits — Southern California permit portals. Equipment matched from permit descriptions.